How do I use Pascal's triangle to expand (x+2)5?

1 Answer

You write out the sixth row of Pascal's triangle and make the appropriate substitutions.

Explanation:

Pascal's triangle is

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The numbers in the fifth row are 1, 5, 10, 10, 5, 1.

They are the coefficients of the terms in a fifth order polynomial.

(x+y)5=x5+5x4y+10x3y2+10x2y3+5xy4+y5

But our polynomial is (x+2)5.

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

(x+2)5=x5+10x4+40x3+80x2+80x+32