1.3x乘x-7x+1=0
x^2-7/3 x=-1/3
(x-7/6)^2=49/36 -1/3
x =7/6±√37/6
2.12x乘x-8x-21=0
x^2-3/4 x=7/4
(x-3/8)^2=7/4 +9/64
x=3/8±11/8 x1=-1,x2=7/4
【【不清楚,再问；满意,祝你好运开☆!】】“^”啥意思