[질문] 2(x+1)(x-1)+(x+2)(x-1) 좀 알려주세요 풀이과정도..

2(x+1)(x-1)+(x+2)(x-1)=0을말하시는거겠죠?좌변을공통인수인(x-1)로묶으면(x-1)(2x+2+x-1)=(x-1)(3x+1)=0,해는x=1,-1/3이나옵니다(괄호안을0으로만드는게해죠)