求答案 数学题目!
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求答案 数学题目!
![求答案 数学题目!](/uploads/image/z/18942218-26-8.jpg?t=%E6%B1%82%E7%AD%94%E6%A1%88+%E6%95%B0%E5%AD%A6%E9%A2%98%E7%9B%AE%21)
18.原式=
两边同时乘以最简公分母(x-1)^2*x
=(x^2-1-x^2/(x-1)^2*x)*x
=-1/(x-1)^2*x)*x
=-1/x^2-2x+1
将x=根号2+1带入原式中
原式=2+1+1=4
19.((x+y)^2/x*(x+y))*x
=2/x *x
=2
20.原式=(2a-a-2)/a^2-4
=(a-2)/(a+2)(a-2)
=1/(a+2)
21. 原式=(2x-x-2)/(x+2)(x-2)*(x+2)/(x-1)
= 1/(x+2)*(x+2)/(x-1)
=1/(x-1)
ok了吧.
两边同时乘以最简公分母(x-1)^2*x
=(x^2-1-x^2/(x-1)^2*x)*x
=-1/(x-1)^2*x)*x
=-1/x^2-2x+1
将x=根号2+1带入原式中
原式=2+1+1=4
19.((x+y)^2/x*(x+y))*x
=2/x *x
=2
20.原式=(2a-a-2)/a^2-4
=(a-2)/(a+2)(a-2)
=1/(a+2)
21. 原式=(2x-x-2)/(x+2)(x-2)*(x+2)/(x-1)
= 1/(x+2)*(x+2)/(x-1)
=1/(x-1)
ok了吧.