已知a²-a-1=0且2a的四次方-3xa²+2/a³+2xa²-a=-93/1

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  • a^2-a-1=0

    a^2-1=a

    a^2=a+1

    (2a^4-3xa^2+2)/(a^3+2xa^2-a)=-93/112

    (2a^4-3xa^2+2)/(a^3+2xa^2-a)

    =[a^2(2a^2-3x)+2] / [a(a^2-1+2xa)]

    ={(a+1)[2(a+1)-3x]+2} / [a(a+2xa)]

    ={2(a+1)^2-3(a+1)x]+2} / [a^2(1+2x)]

    ={2a^2+4a+2-3(a+1)x]+2} / [(a+1)(1+2x)]

    ={2(a+1)+4a+2-3(a+1)x]+2} / [(a+1)(1+2x)]

    ={2(a+1)+4(a+1)-3(a+1)x]} / [(a+1)(1+2x)]

    ={(a+1)(6-3x)} / [(a+1)(1+2x)]

    =3(2-x) / (1+2x)=-93/112

    (2-x) / (1+2x)=-31/112

    112(2-x)=-31(1+2x)

    224-112x=-31-62x

    50x=255

    x=255/50=51/10