20道用配方法解一元二次方程的题

页眉内容

20道用配方法解一元二次方程的题

2乘X平方+3=7X

2x^2+3=7x

2x^2-7x+3=0

x^2-(7/2)x+3/2=0

x^2-(7/2)x=-3/2

x^2-(7/2)x+(7/4)^2=-3/2+(7/4)^2

(x-7/4)^2=-3/2+49/16

(x-7/4)^2=-24/16+49/16

(x-7/4)^2=25/16

(x-7/4)^2=(5/4)^2

x-7/4=±(5/4)

x=7/4±(5/4)

x1=7/4+5/4=12/4=3

x2=7/4-5/4=1/2

页脚内容1