What is the coefficient of x4y4 in the expansion of (x + y)8?

70

Step-by-step explanation:

If you use Pascal's Triangle, you will need 9 lines, since there are 9 terms in a binomial raised to the 8th power.  Those 9 terms are:

1, 8, 28, 56, 70, 56, 28, 8, 1

The first expansion through the one we need are below (I hope you know how to use Pascal's Triangle!):

( - 4 , -7 )

all the lines must parallel  

step-by-step explanation:

coordinates of c = ( - 1 , 2 )

3 units left = ( -4 , 2 )

9 units down = ( - 4 , 11 )