How do you expand (x+2)5 using Pascal’s Triangle?

1 Answer
Dec 31, 2015

x5+10x4+40x3+80x2+80x+32

Explanation:

The 5th row of Pascal's triangle is

1,5,10,10,5,1

These values are the coefficients in a binomial expansion to the 5th power.

(a+b)5=a5+5a4b+10a3b2+10a2b3+5ab4+b5

Notice the pattern of the exponents: the exponent of a starts at 5 and goes to 0, and b starts at 0 and increases to 5.

Apply the rule to (x+2):

(x+2)5=x5+5x4(2)+10x3(22)+10x2(23)+5x(24)+25

x5+10x4+40x3+80x2+80x+32