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Find \(\int_0^1 20x^3 e^{x^4}\) dx.(a) (e-1)(b) 5(e+1)(c) 5e(d) 5(e-1)I had been asked this question during an interview.My question comes from Evaluation of Definite Integrals by Substitution in portion Integrals of Mathematics – Class 12 |
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Answer» RIGHT option is (d) 5(e-1) To explain I would SAY: I=\(\int_0^1 20x^3 e^{X^4}\) dx Let x^4=t Differentiating w.r.t x, we get 4x^3 dx=dt ∴The new limits When x=0, t=0 When x=1,t=1 ∴\(\int_0^1 \,20x^3 \,e^{x^4} \,dx=\int_0^1 5e^t dt\) \(=5[e^t]_0^1=5(e^1-e^0)\)=5(e-1). |
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