How do I use Pascal's triangle to expand (2x+y)4?

1 Answer
Jul 9, 2015

Write out the fifth 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, 4, 6, 4, 1.

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

(x+y)4=x4+4x3y+6x2y2+4xy3+y4

But our polynomial is (2x+y)4.

(2x+y)4=(2x)4+4(2x)3y+6(2x)2y2+4(2x)y3+y4

(2x+y)4=16x4+32x3y+24x2y2+8xy3+y4