Indefinite Integration
Standard integral formulas
Grade 12
Question:
<p><strong>Assertion (A):</strong> When <span class="math">\(f(x) = \frac{x^2 + 1}{2}\)</span>, <span class="math">\(\int \frac{dx}{x} = 2\ln|x| + c\)</span></p><p><strong>Reason (R):</strong> <span class="math">\(\int (h(x))^n h'(x) dx = \frac{(h(x))^{n+1}}{n+1} + C\)</span></p>
<p>(A) Both A and R are true and R is the correct explanation of A</p>
<p>(B) Both A and R are true but R is NOT the correct explanation of A</p>
<p>(C) A is true but R is false</p>
<p>(D) A is false but R is true</p>
Step-by-Step Solution
Key Concept: The standard integral formula for 1/x is independent of auxiliary function definitions; verify formulas carefully
<p><strong>Step 1:</strong> The standard integral <span class="math">$\int \frac{dx}{x} = \ln|x| + c$</span> is independent of the definition of <span class="math">$f(x)$</span></p><p><strong>Step 2:</strong> If <span class="math">$f(x) = \frac{x^2+1}{2}$</span>, this doesn't change the integral of <span class="math">$\frac{1}{x}$</span></p><p><strong>Step 3:</strong> Therefore, <span class="math">$\int \frac{dx}{x} = \ln|x| + c$</span>, not <span class="math">$2\ln|x| + c$</span></p><p><strong>Step 4:</strong> The power rule for composition <span class="math">$(h(x))^n h'(x) dx = \frac{(h(x))^{n+1}}{n+1} + C$</span> is correct</p><p>∴ A is false but R is true.</p>
Correct Answer: B