How do you multiply (x-1)(x+1)(x+2)?

2 Answers
maganbhai P.
Aug 10, 2018

#p(x)=x^3+2x^2-x-2#

Explanation:

Let ,

#p(x)=(x-1)(x+1)(x+2)#

Multiplying first two factors:

#p(x)={x(x+1)-1(x+1)}(x+2)#

#p(x)={x*x+x*1-1*x-1*1}(x+2)#

#p(x)={x^2+cancelx-cancelx-1}(x+2)#

#p(x)=(x^2-1)(x+2)#

Again multiplying two factors :

#p(x)=x^2(x+2)-1(x+2)#

#p(x)=x^2*x+x^2*2-1*x-1*2#

#p(x)=x^3+2x^2-x-2#

Jim G.
Aug 10, 2018

#x^3+2x^2-x-2#

Explanation:

#"given "(x+a)(x+b)(x+c)#

#"then the expansion is"#

#x^3+(a+b+c)x^2+(ab+bc+ac)x+abc#

#"here "a=-1,b=1,c=2#

#=x^3+(-1+1+2)x^2+(-1+2-2)x#
#color(white)(=)+(-1)(1)(2)#

#=x^3+2x^2-x-2#

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