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QJEEM21Ma84cd: JEE Main 2021 Mathematics - Class 12 JEEM21Ma84cd Solution: Let P(x) = x 2 + bx + c be a quadratic polynomial with real…

Let P(x) = x2 + bx + c be a quadratic polynomial with real coefficients such that ∫01P(x)dx\int_0^1 {P(x)dx} = 1 and P(x) leaves remainder 5 when it is divided by (x −- 2). Then the value of 9(b + c) is equal to :

Multiple Choice Options

  • A 9
  • B 11
  • C 7
  • D 15

Step-by-Step Verified Solution

(x−2)Q(x)+5=x2+bx+c(x - 2)Q(x) + 5 = {x^2} + bx + c

Put x = 2

5 = 2b + c + 4 .... (1)

∫01(x2+bx+c)dx=1\int_0^1 {({x^2} + bx + c)dx} = 1

⇒13+b2+c=1\Rightarrow {1 \over 3} + {b \over 2} + c = 1

b2+c=23{b \over 2} + c = {2 \over 3} .... (2)

Solve (1) & (2)

b=29b = {2 \over 9}

c=59c = {5 \over 9}

9(b + c) = 7

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