How do you multiply polynomials (x^2 + 2x - 1)(x^2 + 2x + 5)(x2+2x1)(x2+2x+5)?

2 Answers
Mar 31, 2018

x^4+4x^3+6x^2+8x-5x4+4x3+6x2+8x5

Explanation:

Just use a modified version of foil or a table

x^2(x^2+2x+5)=x^4+2x^3+5x^2x2(x2+2x+5)=x4+2x3+5x2

2x(x^2+2x+5)=2x^3+2x^2+10x2x(x2+2x+5)=2x3+2x2+10x

-1(x^2+2x+5)=-x^2-2x-51(x2+2x+5)=x22x5

Just add them all up

x^4+2x^3+5x^2+2x^3+2x^2+10x-x^2-2x-5x4+2x3+5x2+2x3+2x2+10xx22x5

x^4+color(red)(2x^3+2x^3)+color(blue)(5x^2+2x^2-x^2)+color(pink)(10x-2x)-5x4+2x3+2x3+5x2+2x2x2+10x2x5

x^4+color(red)(4x^3)+color(blue)(6x^2)+color(pink)(8x)-5x4+4x3+6x2+8x5

Mar 31, 2018

x^4+4x^3+8x^2+8x-5x4+4x3+8x2+8x5

Explanation:

Given-

(x^2+2x-1)(x^2+2x+5)(x2+2x1)(x2+2x+5)

(x^2 xx x^2)+(2x xx x^2)-(1 xxx^2)+(x^2 xx 2x)+(2x xx 2x)-(1 xx 2x)+(x^2 xx5)+(2x xx5)-(1xx5)(x2×x2)+(2x×x2)(1×x2)+(x2×2x)+(2x×2x)(1×2x)+(x2×5)+(2x×5)(1×5)

x^4+2x^3-x^2+2x^3+4x^2-2x+5x^2+10x-5x4+2x3x2+2x3+4x22x+5x2+10x5

x^4+2x^3+2x^3-x^2+4x^2+5x^2-2x+10x-5x4+2x3+2x3x2+4x2+5x22x+10x5

x^4+4x^3+8x^2+8x-5x4+4x3+8x2+8x5