已知对于x不等于3且x不等于-2的所有x的值,等式x的平方-x-6分之3x+1=x-3分之A+( x+2)分之B总能成立

4个回答

  • 1、根据题意

    (3x+1)/(x²-x-6)=A/(x-3)+B/(x+2)

    (3x+1)/(x²-x-6)=[A(x+2)+B(x-3)]/[(x-3)(x+2)]

    (3x+1)/(x²-x-6)=(Ax+2A+Bx-3B)/(x²-x-6)

    (3x+1)/(x²-x-6)=[(A+B)x+(2A-3B)]/(x²-x-6)

    A+B=3(1)

    2A-3B=1(2)

    (1)×3+(2)

    5A=10

    A=2

    B=3-A=1

    A=2

    B=1

    2、y=|x-1|/(x-1)-|x-2|/(x-2)+|x²-3x+2|/(3x-x²-2)

    =|x-1|/(x-1)-|x-2|/(x-2)-|(x-2)(x-1)|/(x²-3x+2)

    =|x-1|/(x-1)-|x-2|/(x-2)-|(x-1)(x-2)|/[(x-1)(x-2)]

    零点法

    讨论

    (1)x