Give the 5 and the y the exponent 1 so that every factor inside
the parentheses will have an exponent showing:



Now remove the parentheses by using the "exponential distributive"
principle, i.e multiplying each exponent of each factor inside the 
parentheses by the exponent outside the parentheses on the right:
1 times -2 give -2, -3 times -2 gives +6, 1 times -2 gives -2, and
2 times -2 gives -4, and so far we have:



Now since there are negative exponents, we must get all exponents
positive.  So we put a 1 denominator under that:



Now we move the  from the numerator to the denominator
and change the sign of the -2 exponent to 2.



Next we move the  from the numerator to the denominator
and change the sign of the -2 exponent to 2.



Next we move the  from the numerator to the denominator
and change the sign of the -4 exponent to 4.



Finally we eliminate the 1 factor and change the  to 25




We could have done the last several steps in only one step, but
I thought I'd break it down for you.

Edwin