已知x的2次方+x-1=o求1998x的3次方3996x的2次方的值
问题描述：
已知x的2次方+x-1=o求1998x的3次方3996x的2次方的值
答
∵x²+x-1=0
∴x²=1-x
1998x^3+3996x^2=1998x^3+1998x^2+1998x^2
=1998x(x^2+x)+1998x^2=1998x+1998x^2
=1998(x^2+x)=1998
答
∵x²+x-1=0
∴x²=1-x
所以
1998x³+3996x²
=1998x(1-x)+3996x²
=1998x²+1998x
=1998(x²+1)
=1998×1
=1998
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答
∵x²+x-1=0
∴x²=1-x
所以
1998x³+3996x²
=1998x(1-x)+3996x²
=1998x²+1998x
=1998(x²+1)
=1998×1
=1998
答
解 ：由x^2+x-1=0,得x^2+x=1,
1998x^3+3996x^2=1998x^3+1998x^2+1998x^2
=1998x(x^2+x)+1998x^2=1998x+1998x^2
=1998(x^2+x)=1998