Practice Problems
20 comprehensive problems covering all Module 3 topics
How to Use These Practice Problems
These 20 problems cover all major topics from Module 3. Try to solve each problem on your own before revealing the solution. Work through them systematically to build mastery.
Topics covered: Polynomial functions (end behavior, zeros, graphing), factoring polynomials, rational functions (asymptotes, holes), and inequalities.
Section 1: Polynomial Functions (Problems 1-5)
Determine the end behavior of f(x) = -2x5 + 3x3 - x + 7
Solution
Step 1: Identify degree and leading coefficient
Degree: 5 (odd)
Leading coefficient: -2 (negative)
Step 2: Apply Leading Term Test
Odd degree + Negative leading coefficient:
As x → -∞, f(x) → +∞
As x → +∞, f(x) → -∞
Interpretation: The graph rises on the left and falls on the right.
For f(x) = x(x + 3)2(x - 2)3, identify all zeros, their multiplicities, and graph behavior at each zero.
Solution
| Zero | Multiplicity | Graph Behavior |
|---|---|---|
| x = 0 | 1 (odd) | Crosses x-axis |
| x = -3 | 2 (even) | Touches x-axis (bounces) |
| x = 2 | 3 (odd) | Crosses x-axis (flattens near crossing) |
Additional information:
Total degree: 1 + 2 + 3 = 6 (even)
Leading coefficient: 1 (positive)
End behavior: Both ends point upward
Find all real zeros of f(x) = x3 - 2x2 - 5x + 6
Solution
Step 1: Use Rational Root Theorem
Possible rational roots: ±1, ±2, ±3, ±6
Step 2: Test x = 1
f(1) = 1 - 2 - 5 + 6 = 0 Zero found!
Step 3: Use synthetic division with x = 1
1 | 1 -2 -5 6
| 1 -1 -6
|___________________
1 -1 -6 0
Quotient: x2 - x - 6
Step 4: Factor the quotient
x2 - x - 6 = (x - 3)(x + 2)
Step 5: Complete factorization
f(x) = (x - 1)(x - 3)(x + 2)
All zeros: x = -2, 1, 3
Sketch the graph of f(x) = -x3 + 4x. Include zeros, y-intercept, and end behavior.
Solution
Step 1: Factor to find zeros
f(x) = -x3 + 4x = -x(x2 - 4) = -x(x - 2)(x + 2)
Zeros: x = -2, 0, 2 (all multiplicity 1, so graph crosses at each)
Step 2: Find y-intercept
f(0) = 0, so y-intercept is (0, 0)
Step 3: Determine end behavior
Degree: 3 (odd), Leading coefficient: -1 (negative)
As x → -∞, f(x) → +∞
As x → +∞, f(x) → -∞
Step 4: Test points
f(-3) = -(-27) + 12 = 39 (positive)
f(1) = -1 + 4 = 3 (positive)
f(3) = -27 + 12 = -15 (negative)
Graph characteristics:
- Comes from upper left (positive infinity)
- Crosses at x = -2
- Goes up to a local maximum between -2 and 0
- Crosses at x = 0
- Goes down to a local minimum between 0 and 2
- Crosses at x = 2
- Continues down to negative infinity
A polynomial f(x) has degree 4 with leading coefficient 3. It has zeros at x = -1 (multiplicity 2) and x = 2 (multiplicity 2). Write the polynomial in factored form and determine its end behavior.
Solution
Step 1: Write in factored form
f(x) = 3(x + 1)2(x - 2)2
Step 2: Verify degree
Degree = 2 + 2 = 4
Step 3: Determine end behavior
Degree: 4 (even)
Leading coefficient: 3 (positive)
As x → -∞, f(x) → +∞
As x → +∞, f(x) → +∞
Both ends point upward.
Additional notes:
Graph touches (bounces) at both x = -1 and x = 2 (even multiplicities)
The graph never crosses the x-axis; it touches at two points and is positive everywhere else
Section 2: Factoring Polynomials (Problems 6-10)
Factor completely: 8x3 + 27
Solution
Step 1: Recognize as sum of cubes
8x3 + 27 = (2x)3 + 33
Step 2: Apply sum of cubes formula
a3 + b3 = (a + b)(a2 - ab + b2)
where a = 2x and b = 3
Step 3: Substitute
(2x + 3)[(2x)2 - (2x)(3) + 32]
(2x + 3)(4x2 - 6x + 9)
Answer: (2x + 3)(4x2 - 6x + 9)
Factor: 3x3 - 6x2 + 4x - 8
Solution
Step 1: Group terms in pairs
(3x3 - 6x2) + (4x - 8)
Step 2: Factor GCF from each group
3x2(x - 2) + 4(x - 2)
Step 3: Factor out common binomial
(x - 2)(3x2 + 4)
Answer: (x - 2)(3x2 + 4)
Note: 3x2 + 4 cannot be factored further over the real numbers
Factor completely: 64x3 - 1
Solution
Step 1: Recognize as difference of cubes
64x3 - 1 = (4x)3 - 13
Step 2: Apply difference of cubes formula
a3 - b3 = (a - b)(a2 + ab + b2)
where a = 4x and b = 1
Step 3: Substitute
(4x - 1)[(4x)2 + (4x)(1) + 12]
(4x - 1)(16x2 + 4x + 1)
Answer: (4x - 1)(16x2 + 4x + 1)
Use the Rational Root Theorem to find all real zeros of f(x) = 2x3 - x2 - 13x - 6
Solution
Step 1: List potential rational zeros
p (factors of -6): ±1, ±2, ±3, ±6
q (factors of 2): ±1, ±2
Potential zeros: ±1, ±2, ±3, ±6, ±1/2, ±3/2
Step 2: Test x = -2
f(-2) = 2(-8) - 4 - 13(-2) - 6 = -16 - 4 + 26 - 6 = 0
Step 3: Synthetic division with x = -2
-2 | 2 -1 -13 -6
| -4 10 6
|___________________
2 -5 -3 0
Quotient: 2x2 - 5x - 3
Step 4: Factor the quotient
2x2 - 5x - 3 = (2x + 1)(x - 3)
Step 5: Complete factorization
f(x) = (x + 2)(2x + 1)(x - 3)
All zeros: x = -2, x = -1/2, x = 3
Factor completely: 2x4 - 162
Solution
Step 1: Factor out GCF
2x4 - 162 = 2(x4 - 81)
Step 2: Recognize difference of squares
x4 - 81 = (x2)2 - 92 = (x2 - 9)(x2 + 9)
Step 3: Factor x2 - 9 further (difference of squares)
x2 - 9 = (x - 3)(x + 3)
Step 4: Complete factorization
Answer: 2(x - 3)(x + 3)(x2 + 9)
Note: x2 + 9 cannot be factored over the real numbers
Section 3: Rational Functions (Problems 11-15)
Find all vertical and horizontal asymptotes of f(x) = (3x2 - 12)/(x2 + x - 6)
Solution
Step 1: Factor numerator and denominator
Numerator: 3x2 - 12 = 3(x2 - 4) = 3(x - 2)(x + 2)
Denominator: x2 + x - 6 = (x + 3)(x - 2)
Step 2: Cancel common factors
f(x) = 3(x + 2)/(x + 3), x ≠ 2
Step 3: Find vertical asymptotes
Set remaining denominator = 0: x + 3 = 0
Vertical asymptote: x = -3
Step 4: Find horizontal asymptote
After cancellation: degree of numerator = 1, degree of denominator = 1
Leading coefficients: 3/1
Horizontal asymptote: y = 3
Note: x = 2 creates a hole, not a vertical asymptote
Find all holes in the graph of g(x) = (x2 + 5x + 6)/(x2 - 4)
Solution
Step 1: Factor completely
Numerator: x2 + 5x + 6 = (x + 2)(x + 3)
Denominator: x2 - 4 = (x - 2)(x + 2)
Step 2: Identify common factors
Common factor: (x + 2)
Step 3: Cancel common factor
g(x) = (x + 3)/(x - 2), x ≠ -2
Step 4: Find x-coordinate of hole
x + 2 = 0 → x = -2
Step 5: Find y-coordinate using simplified function
y = (-2 + 3)/(-2 - 2) = 1/(-4) = -1/4
Hole at: (-2, -1/4)
Vertical asymptote at: x = 2
Find the domain of h(x) = (x + 5)/(x2 - 2x - 15)
Solution
Step 1: Set denominator equal to zero
x2 - 2x - 15 = 0
Step 2: Factor
(x - 5)(x + 3) = 0
Step 3: Solve
x = 5 or x = -3
Step 4: State domain
Domain: All real numbers except x = -3 and x = 5
Interval notation: (-∞, -3) ∪ (-3, 5) ∪ (5, ∞)
Set notation: {x | x ≠ -3, x ≠ 5}
Find all asymptotes, holes, and intercepts of f(x) = (2x2 - 8)/(x2 + 3x + 2)
Solution
Step 1: Factor
Numerator: 2x2 - 8 = 2(x2 - 4) = 2(x - 2)(x + 2)
Denominator: x2 + 3x + 2 = (x + 1)(x + 2)
Step 2: Simplify
f(x) = 2(x - 2)/(x + 1), x ≠ -2
Step 3: Find hole
Hole at x = -2, y = 2(-2 - 2)/(-2 + 1) = 2(-4)/(-1) = 8
Hole: (-2, 8)
Step 4: Find vertical asymptote
x + 1 = 0 → x = -1
Vertical asymptote: x = -1
Step 5: Find horizontal asymptote
After simplification: degree 1/degree 1, coefficients 2/1
Horizontal asymptote: y = 2
Step 6: Find x-intercept (set numerator = 0)
2(x - 2) = 0 → x = 2
X-intercept: (2, 0)
Step 7: Find y-intercept (evaluate f(0))
f(0) = 2(0 - 2)/(0 + 1) = -4/1 = -4
Y-intercept: (0, -4)
Determine the horizontal asymptote of f(x) = (5x3 - 2x + 1)/(3x3 + 7x2 - 4)
Solution
Step 1: Compare degrees
Degree of numerator: 3
Degree of denominator: 3
Degrees are equal
Step 2: Find ratio of leading coefficients
Leading coefficient of numerator: 5
Leading coefficient of denominator: 3
Ratio: 5/3
Horizontal asymptote: y = 5/3
Interpretation: As x → ±∞, f(x) → 5/3
Section 4: Inequalities (Problems 16-20)
Solve: x2 - 7x + 10 < 0
Solution
Step 1: Factor
x2 - 7x + 10 = (x - 2)(x - 5)
Step 2: Find critical values
x = 2 and x = 5
Step 3: Test intervals
| Interval | Test Point | Sign |
|---|---|---|
| (-∞, 2) | x = 0 | (-)(-) = + |
| (2, 5) | x = 3 | (+)(-) = - |
| (5, ∞) | x = 6 | (+)(+) = + |
Step 4: Select negative interval
We want f(x) < 0 (negative)
Solution: (2, 5)
Or: 2 < x < 5
Solve: x3 + 2x2 - 3x ≥ 0
Solution
Step 1: Factor
x3 + 2x2 - 3x = x(x2 + 2x - 3) = x(x + 3)(x - 1)
Step 2: Find zeros
x = -3, 0, 1
Step 3: Create sign chart
Interval: (-∞,-3) | (-3,0) | (0,1) | (1,∞) Sign: - | + | - | +
Step 4: We want f(x) ≥ 0 (positive or zero)
Positive intervals: (-3, 0) and (1, ∞)
Include boundaries (≥): x = -3, 0, 1
Solution: [-3, 0] ∪ [1, ∞)
Solve: (x - 4)/(x + 1) > 0
Solution
Step 1: Find critical values
Numerator = 0: x = 4
Denominator = 0: x = -1
Step 2: Test intervals
| Interval | Test Point | Sign |
|---|---|---|
| (-∞, -1) | x = -2 | (-)/(-) = + |
| (-1, 4) | x = 0 | (-)/(+) = - |
| (4, ∞) | x = 5 | (+)/(+) = + |
Step 3: Select positive intervals
We want f(x) > 0 (positive)
Do not include x = -1 (makes denominator zero)
Do not include x = 4 (strict inequality >)
Solution: (-∞, -1) ∪ (4, ∞)
Solve: (x2 - 9)/(x - 1) ≤ 0
Solution
Step 1: Factor numerator
(x2 - 9)/(x - 1) = (x - 3)(x + 3)/(x - 1)
Step 2: Find critical values
From numerator: x = -3, 3
From denominator: x = 1
All critical values: -3, 1, 3
Step 3: Create sign chart
Interval: (-∞,-3) | (-3,1) | (1,3) | (3,∞) Sign: - | + | - | +
Step 4: We want f(x) ≤ 0 (negative or zero)
Negative intervals: (-∞, -3) and (1, 3)
Include x = -3 and x = 3 (≤ and denominator ≠ 0)
Never include x = 1 (denominator = 0)
Solution: (-∞, -3] ∪ (1, 3]
Solve: x(x - 2)2(x + 1) > 0
Solution
Step 1: Identify zeros and multiplicities
x = 0 (multiplicity 1 - odd)
x = 2 (multiplicity 2 - even)
x = -1 (multiplicity 1 - odd)
Step 2: Key insight
Sign changes at odd multiplicity zeros (0 and -1)
Sign does NOT change at even multiplicity zero (2)
Step 3: Create sign chart
Interval: (-∞,-1) | (-1,0) | (0,2) | (2,∞) Factor x: - | - | + | + Factor(x-2)²: + | + | + | + Factor(x+1): - | + | + | + Product: + | - | + | +
Step 4: Select positive intervals
We want f(x) > 0 (positive)
Positive intervals: (-∞, -1), (0, 2), and (2, ∞)
Note: (0, 2) and (2, ∞) can be combined as (0, ∞)
Solution: (-∞, -1) ∪ (0, ∞)
Or: x < -1 or x > 0
Practice Complete!
Congratulations on working through all 20 practice problems! You've covered all major topics from Module 3.
Next steps: Take the Module Quiz to test your understanding, then review the Study Guide to prepare for exams.