己知代数式4x²-2x+2的值是4,试求代数式2x²-x+1的值若x²+x-1=0,试求代数式x三次方+2x²-7的值,
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![己知代数式4x²-2x+2的值是4,试求代数式2x²-x+1的值若x²+x-1=0,试求代数式x三次方+2x²-7的值,](/uploads/image/z/4111682-50-2.jpg?t=%E5%B7%B1%E7%9F%A5%E4%BB%A3%E6%95%B0%E5%BC%8F4x%26%23178%3B-2x%2B2%E7%9A%84%E5%80%BC%E6%98%AF4%2C%E8%AF%95%E6%B1%82%E4%BB%A3%E6%95%B0%E5%BC%8F2x%26%23178%3B-x%2B1%E7%9A%84%E5%80%BC%E8%8B%A5x%26%23178%3B%2Bx-1%3D0%2C%E8%AF%95%E6%B1%82%E4%BB%A3%E6%95%B0%E5%BC%8Fx%E4%B8%89%E6%AC%A1%E6%96%B9%2B2x%26%23178%3B-7%E7%9A%84%E5%80%BC%2C)
己知代数式4x²-2x+2的值是4,试求代数式2x²-x+1的值若x²+x-1=0,试求代数式x三次方+2x²-7的值,
己知代数式4x²-2x+2的值是4,试求代数式2x²-x+1的值
若x²+x-1=0,试求代数式x三次方+2x²-7的值,
己知代数式4x²-2x+2的值是4,试求代数式2x²-x+1的值若x²+x-1=0,试求代数式x三次方+2x²-7的值,
己知代数式4x²-2x+2的值是4,试求代数式2x²-x+1的值
4x²-2x+2=4
两边同除以2得:
2x²-x+1=2
若x²+x-1=0,试求代数式x三次方+2x²-7的值
x²+x-1=0
x²+x=1
∴x³+2x²-7
=x³+x²+x²-7
=x(x²+x)+x²-7
=x+x²-7
=1-7
=-6
代数式4x²-2x+2的值是4,代数式2x²-x+1的值=4*1/2=2
若x²+x-1=0,试求代数式x三次方+2x²-7的值,
x^2=1-x
x^3=x-x^2
x^3+2x^2-7
=x-x^2+2x^2-7
=x^2+x-7
=1-7
=-6
考察的是整体思想,因为4x²-2x+2=4,把4x²-2x看成一个整体,所以4x²-2x=2,所以2x²-x=1,则2x²-x+1=2;同理x²+x=1,则原式=x^3+x²+x²-7=x(x²+x)+x²-7=x+x²-7=-6