Differentiation - 15 Multiple Choice + 6 Free Response Questions
Recommended time: 45 minutes
Solution:
1) Let g(x) = x² + 3x (inside function)
2) Let f(u) = u⁴ (outside function)
3) g'(x) = 2x + 3
4) f'(u) = 4u³
5) Using chain rule: f'(x) = f'(g(x)) · g'(x)
6) f'(x) = 4(x² + 3x)³ · (2x + 3)
Answer: 4(x² + 3x)³(2x + 3)
Solution:
1) Let f(x) = x² + 1 and g(x) = x - 2
2) f'(x) = 2x and g'(x) = 1
3) Using quotient rule: d/dx[f(x)/g(x)] = [f'(x)g(x) - f(x)g'(x)]/[g(x)]²
4) = [(2x)(x - 2) - (x² + 1)(1)]/(x - 2)²
5) = [2x² - 4x - x² - 1]/(x - 2)²
6) = (x² - 4x - 1)/(x - 2)²
Answer: (x² - 4x - 1)/(x - 2)²
Solution:
1) Let g(x) = x² + 1 (inside function)
2) Let f(u) = sin(u) (outside function)
3) g'(x) = 2x
4) f'(u) = cos(u)
5) Using chain rule: f'(x) = f'(g(x)) · g'(x)
6) f'(x) = cos(x² + 1) · 2x
Answer: 2x cos(x² + 1)
Solution:
1) Let f(x) = x² and g(x) = e^(3x)
2) f'(x) = 2x
3) g'(x) = 3e^(3x) (using chain rule)
4) Using product rule: d/dx[f(x)g(x)] = f'(x)g(x) + f(x)g'(x)
5) = (2x)(e^(3x)) + (x²)(3e^(3x))
6) = e^(3x)(2x + 3x²)
Answer: e^(3x)(2x + 3x²)
Solution:
1) Let g(x) = x² + 2x + 1 (inside function)
2) Let f(u) = ln(u) (outside function)
3) g'(x) = 2x + 2
4) f'(u) = 1/u
5) Using chain rule: f'(x) = f'(g(x)) · g'(x)
6) f'(x) = (1/(x² + 2x + 1)) · (2x + 2)
7) = (2x + 2)/(x² + 2x + 1)
8) = 2(x + 1)/(x + 1)² = 2/(x + 1)
Answer: 2/(x + 1)
Solution:
1) Let f(x) = (x³ + 1)² and g(x) = x² - 1
2) First find f'(x) using chain rule: f'(x) = 2(x³ + 1) · 3x² = 6x²(x³ + 1)
3) g'(x) = 2x
4) Using product rule: d/dx[f(x)g(x)] = f'(x)g(x) + f(x)g'(x)
5) = [6x²(x³ + 1)](x² - 1) + (x³ + 1)²(2x)
6) = 6x²(x³ + 1)(x² - 1) + 2x(x³ + 1)²
7) = (x³ + 1)[6x²(x² - 1) + 2x(x³ + 1)]
8) = (x³ + 1)[6x⁴ - 6x² + 2x⁴ + 2x]
9) = (x³ + 1)(8x⁴ - 6x² + 2x)
Answer: (x³ + 1)(8x⁴ - 6x² + 2x)