(1)6x＾2-7x+1=0
（6x-1）（x-1）=0
x1=1/6 x2=1
(2)5x＾2-18=9x
5x^2-9x-18=0
(5x+6)(x-3)=0
x1=-6/5 x2=3
(3)4x＾2-3x=52
4x^2-3x-52=0
(4x+13)(x-4)=0
x1=-13/4 x2=4
(4)5x＾2=4-2x.
5x^2+2x=4
x^2+0.4x=0.8
x^2+0.4x+0.04=0.84
(x+0.2)^2=21/25
x+1/5=±√21/5
x=-1/5±√21/5
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