Q59 / 160 · TS EAMCET 2021 (04 Aug Shift 1) · Mathematics

For any quadratic polynomial f(x), it is true that
fx=fa+f'a(x-a)+f"a2!x-a2 where a is any real number.
If 3x2+4x+7(x-2)3=A(x-2)3+B(x-2)2+C(x-2) and g(x)=3x2+4x+7 then A+B+C=

  • A
    g(2)+g'(2)+g"(2)
  • B
    g"2+2g2+g'12!
  • Correct answer
    C
    g2+g'2+g"22!
  • D
    2g2+2g'2+g"22!

Solution

3x2+4x+7(x-2)3=A(x-2)3+B(x-2)2+C(x-2) is the given equation, which can be written as,

3x2+4x+7=A+B(x-2)+C(x-2)2

3x2+4x+7=A+B(x-2)+C(x2-4x+4)

Comparing the coefficients we get,

A-2B+4C=7 (coefficients of constants)B-4C=4 (coefficients of x)C=3 (coefficients of x2)

Solving the equations we get, A=3,B=4,C=16

A+B+C=46

from given,

g(x)=3x2+4x+7 ⇒ g(2)=27

g'(x)=6x+4⇒g'(2)=16

g''(x)=6

Comparing from options, g2+g'2+g"22!=46

Hence, it is the required answer.

 

Hence, the correct answer is option: 'C'.

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