5x^2-18=9x
x^2-9x/5=18/5
(x-9/10)^2=18/5+81/100
(x-9/10)^2=441/100
x-9/10=21/10
x1=31/10
x-9/10=-21/10
x2=-6/5
所以原方程的解是:x1=31/10 x2=-6/5
4x^2-3x=52
x^2-3x/4=13
(x-3/8)^2=13+9/64
(x-3/8)^2=(29/8)^2
x-3/8=29/8
x1=4
x-3/8=-29/8
x2=-13/4
所以:原方程的解是:x1=4 x2=-13/4
5x^2=4-2x
x^2+2x/5=4/5
(x+1/5)^2=4/5+1/25
(x+1/5)^2=21/25
x+1/5=根号21/5
x1=根号21/5-1/5
x+1/5=-根号21/5
x2=-根号21/5-1/5
所以原方程的解是:
x1=根号21/5-1/5
x2=-根号21/5-1/5