初中数学想先化简再求值

2024-10-31 22:16:27

推荐回答（3个）

回答1：

=[x²/(x-2)-4/(x-2)]×1/x(x+2)
=(x²-4)/(x-2)×1/x(x+2))
=(x+2)(x-2)/(x-2)×1/x(x+2)
=1/x
当x=√2-1时
原式=1/（√2-1）=√2+1

回答2：

原式=[x²/(x-2)-4/(x-2)]*1/x(x+2)
=(x²-4)/(x-2)*1/x(x+2)
=(x+2)(x-2)/(x-2)*1/x(x+2)
=(x+2)*1/x(x+2)
=1/x
=1/(√2-1)
=√2+1

回答3：

=[x²/(x-2) + (-4)/(x-2)] ·1/(x²+2x)
=(x²-4)/(x-2) ·1/(x²+2x)
=(x+2)(x-2)/(x-2) ·1/(x²+2x)
=(x+2)/x(x+2)
=1/x

初中数学 想先化简再求值