Q.

Let I1=∫0xetx.e-t2dt and I2=∫0xe-t2/4dt where x>0, then the value of I1I2 is

1 e-x2/2  
2 ex2/4  
3 e-x2/4  
4 ex2/2  

Ans.

(2)

I1=∫0xex24-(t-x2)2dt=ex24∫-x2x2e-z2dz    t-x2=z

=2ex24∫0x2e-z2dz

I2=∫0xe-t24dt

Let t2=z  =∫0x2e-z2×2dz