Question Details

Let  f (x) = x 3 + x 2 f (1) + 2 x f (2) + f (3), x R . Then the value of f (5)  is

Options

A

1175

B

625

C

6575

D

25

Show Answer

Correct Answer :

Option A

1175

Solution :

The correct answer is 1175.

Step-by-step Explanation:

Given the function:
f(x)=x3+x2f(1)+2xf(2)+f(3)

Notice that f(1), f(2), and f(3) are constant values. Let us define them as:
a=f(1)
b=f(2)
c=f(3)

Rewriting the function f(x) using these constants:
f(x)=x3+ax2+2bx+c

Now, let us find the first, second, and third derivatives of f(x) with respect to x:

1. First Derivative:
f(x)=3x2+2ax+2b

2. Second Derivative:
f(x)=6x+2a

3. Third Derivative:
f(x)=6

Now, substitute the values of x=3, x=2, and x=1 into their respective derivatives to find the constants:

From the third derivative:
c=f(3)=6

From the second derivative at x=2:
b=f(2)=6(2)+2a=12+2a

From the first derivative at x=1:
=f(1)=3(12)+2a(1)+2b
a=3+2a+2b
a+2b+3=0

Substitute b=12+2a into the equation a+2b+3=0:
a+2(12+2a)+3=0
a+24+4a+3=0
5a+27=0
a=-275

Now, determine the value of b:
b=12+2-275=12-545=65

Finally, we calculate f(5):
f(5)=3(52)+2a(5)+2b
f(5)=75+10a+2b
f(5)=75+10-275+265
f(5)=75-54+125
f(5)=21+125=105+125=1175

Thus, the value of f(5) is equal to 1175.

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