Question

化简:a平方-9分之2a-a-3分之1

再解一题:已知X平方-2=0，求x平方-1分之(x-1)平方+x+1分之x平方的值

Answer 1

a平方-9分之2a-a-3分之1
=2a/[(a+3)(a-3]-(a+3)/[(a+3)(a-3)]
=(a-3)/[(a+3)(a-3)]
=1/(a+3)

x^2=2
x平方-1分之(x-1)平方+x+1分之x平方
=[(x-1)^2+x^2(x-1)/(x^2-1)
=[(x-1)^2+2(x-1)/(x^2-1)
=(x^2-1)/(x^2-1)
=1

Answer 2

x²—（x—1）+x+x²
=2x²—x+1+x
=2x²—2x+1
当x²=2时
原式=2·2—2x+1
=4—2x+1
=3+2x