JEE Main202628 January 2026Morning ShiftMathematicsDefinite IntegrationActual
Let f be a polynomial function such that f (x²+1 )=x⁴+5 x²+2 , for all x R . Then ₀³ f(x) d x is equal to
Options
- A5 3
- B41 3
- C27 2
- D33 2
Correct answer
D. 33 2
Step-by-step solution
Let u = x^2 + 1 , then x^2 = u - 1 . Substituting into the given condition: f(u) = (u-1)^2 + 5(u-1) + 2 = u^2 - 2u + 1 + 5u - 5 + 2 = u^2 + 3u - 2 . Therefore, f(x) = x^2 + 3x - 2 . Calculating the integral: ₀^3 f(x)dx = ₀^3 (x^2 + 3x - 2)dx = [ x^3 3 + 3x^2 2 - 2x ]₀^3 = 9 + 27 2 - 6 = 33 2 .