So, for this kind of problem you need to FOIL.
This stands for:
F- first
O-outer
I-inner
L-last
What this means is that:
step 1- multiply the FIRST terms in each thing. So for example in problem 6 of the problems you sent it would be x times x. =
step 2- multiply the OUTER terms in each thing. So for example in problem 6, it would be x times 3. =3x
step 3- multiply the INNER terms in each thing. So for example in problem 6, it would be 6 times x. =6x
step 4- multiply the LAST terms in each thing. So for example in problem 6, it would be 6 times 3. =18
step 5: you add all of your products. So for problem 6 it would be y=
+ 9x +18.
Answer:
10
Step-by-step explanation:
The new area is (x-2)(y-2), the area is xy-2(x+y)+4, and the difference is 2(x+y)-4, which is 26. x+y=15, so the perimeter is 2*15=30 feet.