You don't need a substitution. See here.
By making use of the change of variable y = x + 3 write the integral below in a form where the range of integration is
All I know to do is to substitute x + 3 into the integral where y is. I'd guess minusing 3 from the x + 3 could be what's required to have the integral in the form where the range is .
Then make it into a definite integral.
Yes, replace every y in the integrand with x+ 3: and . When y= 3, x= 0 so the lower limit is 0. As y goes to infinity so does x= y+ 3, so the upper limit is infinity. Of course, with y= x+ 3, dy= dx.
(By the way "minusing" is not a word in the English language. Use "subtracting" instead.)