Question

（40-x)(20+5x)=1600的解法

Answer 1

（40-x)(20+5x)=1600800+200X-20X-5X2=1600-5X2+180X-800=0-X2+36X-160=0X2-36X+160=0X2-36X+324-164=0(X-18)2-164=0(X-18)2=164X-18=±9√2X=18±9√2