Mathematics › Definite Integration › Properties of Definite Integration
Given,∫0115+2x-2x21+e2-4xdx=1αlogeα+1βNow let,I=12∫01152-x2-x1+e-4x-12dx⇒I=12∫011114-x-1221+e-4x-12dxNow let x-12=t⇒dx=dtSo, integral becomes,I=12∫-121211122-t21+e-4tdt⇒I=12∫-12011122-t21+e-4tdt+12∫01211122-t21+e-4tdt⏟I2Now solving I2=12∫-121211122-t21+e-4tdt, Let t=-z, we get dt=-dzSo, I2=-12∫120dz1122-z21+e4z⇒I2=12∫012dt1122-t21+e4tNow putting the value of I2 in I we get,I=12∫01211122-t21+e-4t+11122-t21+e4tdt⇒I=12∫012e4t1122-t2e4t+1+11122-t21+e4tdt⇒I=12∫01211122-t2dt⇒I=12×12112ln112+t112-t012⇒I=1211ln11+111-1=1211ln(11+1)210⇒I=111ln11+110Now on comparing with 1αlogeα+1β we get,⇒α=11, β=10⇒α4-β4=21
Given,
∫0115+2x-2x21+e2-4xdx=1αlogeα+1β
Now let,
I=12∫01152-x2-x1+e-4x-12dx
⇒I=12∫011114-x-1221+e-4x-12dx
Now let x-12=t⇒dx=dt
So, integral becomes,
I=12∫-121211122-t21+e-4tdt
⇒I=12∫-12011122-t21+e-4tdt+12∫01211122-t21+e-4tdt⏟I2
Now solving I2=12∫-121211122-t21+e-4tdt,
Let t=-z, we get dt=-dz
So, I2=-12∫120dz1122-z21+e4z
⇒I2=12∫012dt1122-t21+e4t
Now putting the value of I2 in I we get,
I=12∫01211122-t21+e-4t+11122-t21+e4tdt
⇒I=12∫012e4t1122-t2e4t+1+11122-t21+e4tdt
⇒I=12∫01211122-t2dt
⇒I=12×12112ln112+t112-t012
⇒I=1211ln11+111-1=1211ln(11+1)210
⇒I=111ln11+110
Now on comparing with 1αlogeα+1β we get,
⇒α=11, β=10⇒α4-β4=21
Asked in: JEE Main 2023 (15 Apr Shift 1)
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