解方程5x^2-8(3-x)-72=0,

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  • 5x^2-8(3-x)^2-72=0 ==》 5x^2-8(9+x^2-6x)-72=0 ==》-3x^2+48x-144=0 ==》3x^2-48x+144=0 ==》(3x-12)(x-12)=0 ==》x=12或x=4

    2x^2+3x+1=0 ==》 (√2x+(3/4)*√2)^2=(3√2-4)/4 ==》√2x+(3/4)*√2=√((3√2-4)/4) ==》√2x+(3/4) √2=√(3√2-4)/2 ==》x=-√2

    2x^2-3x-1=0 ==》△=9+8=17>0 ==》x=(3±√17)/4

    (x+1)(x+8)=12 ==》x^2+9x-4=0 ==》△=81+8>0 ==》x=(9±√89)/4

    (1-3y)^2+2(3y-1)=0 ==》 9y^2+6x-7=0 ==》△=36+4*7*9>0 ==》y=(6±√288)/18