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Find: ∫(x+3)3-4x-x2dx

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Question

Find: `int(x+3)sqrt(3-4x-x^2dx)`

Sum
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Solution

`I=int(x+3)sqrt(3-4x-x^2)dx`

Let (x + 3) = `A*d/dx(3-4x-x^2)+B `

⇒ x + 3 = A(−2x − 4) + B

⇒ x + 3 = −2Ax − 4A + B

∴ −2A = 1

⇒ A = `-1/2`

⇒ −4A + B = 3

⇒ `-4(-1/2)+B=3`

⇒ B = 1

`:.I=int[-1/2*d/dx(3-4x-x^2)+1]sqrt(3-4x-x^2dx)`

`=1/2intd/dx(3-4x-x^2)sqrt(3-4x-x^2)dx+intsqrt(3-4x-x^2-4+4)dx`

`=1/2((3-4x-x^2)^(3/2)/(3/2))+intsqrt(7-(x+2)^2)dx`

 `= -(3-4x-x^2)^(3/2)/3+(x+2)/2sqrt(7-(x+2)^2)+7/2sin^(-1)((x+2)/sqrt7)+C`

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2015-2016 (March) All India Set 1 N
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