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JEE Main
Exam
JEE Main
Subject
Mathematics
Chapter
Differentiation

JEE Main · Mathematics · Differentiation

Let f(x) and g(x) be polynomials defined as f(x) = x^2 + x g'(1) +...

Let f(x)f(x) and g(x)g(x) be polynomials defined as f(x)=x2+xg′(1)+g′′(2)f(x) = x^2 + x g'(1) + g''(2) and g(x)=x3+x2f′(1)+xf′′(2)g(x) = x^3 + x^2 f'(1) + x f''(2) for all x∈Rx \in \mathbb{R}. The value of f(10)+g(10)f(10) + g(10) is equal to

Correct answer

328

Step-by-step solution

Given the functions:
f(x)=x2+xg′(1)+g′′(2)f(x) = x^2 + x g'(1) + g''(2)
g(x)=x3+x2f′(1)+xf′′(2)g(x) = x^3 + x^2 f'(1) + x f''(2)

Differentiating f(x)f(x) with respect to xx:
f′(x)=2x+g′(1)f'(x) = 2x + g'(1)
f′′(x)=2f''(x) = 2
Thus, f′′(2)=2f''(2) = 2.

Substitute f′′(2)=2f''(2) = 2 into g(x)g(x):
g(x)=x3+x2f′(1)+2xg(x) = x^3 + x^2 f'(1) + 2x

Differentiating g(x)g(x) with respect to xx:
g′(x)=3x2+2xf′(1)+2g'(x) = 3x^2 + 2x f'(1) + 2
g′′(x)=6x+2f′(1)g''(x) = 6x + 2f'(1)

Evaluate g′(x)g'(x) at x=1x = 1 and g′′(x)g''(x) at x=2x = 2:
g′(1)=3(1)2+2(1)f′(1)+2=5+2f′(1)g'(1) = 3(1)^2 + 2(1)f'(1) + 2 = 5 + 2f'(1)
g′′(2)=6(2)+2f′(1)=12+2f′(1)g''(2) = 6(2) + 2f'(1) = 12 + 2f'(1)

Now, evaluate f′(x)=2x+g′(1)f'(x) = 2x + g'(1) at x=1x = 1:
f′(1)=2(1)+g′(1)f'(1) = 2(1) + g'(1)
Substitute g′(1)=5+2f′(1)g'(1) = 5 + 2f'(1) into this equation:
f′(1)=2+5+2f′(1)f'(1) = 2 + 5 + 2f'(1)
f′(1)=7+2f′(1)f'(1) = 7 + 2f'(1)
⇒f′(1)=−7\Rightarrow f'(1) = -7

Using f′(1)=−7f'(1) = -7, we find g′(1)g'(1) and g′′(2)g''(2):
g′(1)=5+2(−7)=−9g'(1) = 5 + 2(-7) = -9
g′′(2)=12+2(−7)=−2g''(2) = 12 + 2(-7) = -2

Substitute these values back to construct f(x)f(x) and g(x)g(x):
f(x)=x2−9x−2f(x) = x^2 - 9x - 2
g(x)=x3−7x2+2xg(x) = x^3 - 7x^2 + 2x

Evaluate both functions at x=10x = 10:
f(10)=(10)2−9(10)−2=100−90−2=8f(10) = (10)^2 - 9(10) - 2 = 100 - 90 - 2 = 8
g(10)=(10)3−7(10)2+2(10)=1000−700+20=320g(10) = (10)^3 - 7(10)^2 + 2(10) = 1000 - 700 + 20 = 320

Finally, the sum is:
f(10)+g(10)=8+320=328f(10) + g(10) = 8 + 320 = 328.

Answer: 328328
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