Hello, I really need some help

I have the utility function: U(x1,x2)=x1^a*x2^1-a

And I have the budget constraint: p1x1^a+p2x2^1-a=m

I have to show that by finding the maximum for the resulting expression with respect to x1 (ie by differentiating with respect to x1 and setting equal to zero), etc., that the optimal consumption bundle for the consumer is:

x1=am/p1 and x2=(1-a)m/p2

Can somebody please help me