麻烦各位帮我解个一元二次方程吧5x(x-3)=21-7x2x^2-5x+1=03x^2+7x+2=0_数学解答

麻烦各位帮我解个一元二次方程吧
5x(x-3)=21-7x
2x^2-5x+1=0
3x^2+7x+2=0

人气：132 ℃　时间：2020-06-27 01:31:33

解答

(1) 5x(x-3)=21-7x
=>5x^2-8x-21=0
=>(x+3)(5x-7)=0
=>x=-3 or x=7/5
2x^2-3x+1=0
=>(x-1)(2x-1)=0
=>x=1 or x=1/2
3x^2+7x+2=0
=>(x+2)(3x+1)=0
=>x=-2 or x=-1/3