Question

1.当x=-时( - 是什么意思我也不懂),分式2x-y分之x+y的值为零,求此时2x-y的值

Answer 1

1.

分式2x-y分之x+y的值为零,

此时x=-y

2x-y=-3y

2.

令x/3=y/4=z/6=t

x=3t,y=4t,z=6t

x-y+z分之x+y-z=(3t+4t-6t)/(3t-4t+7t)=1/6

3.

2/(x+3)+2/(3-x)+(2x+18)/(x²-9)

=（2x-6-2x-6+2x+18）/(x+3)(x-3)

=(2x+6)/(x+3)(x-3)

=2/(x-3)

因为是整数,所以

x-3=2,x=5

x-3=-2,x=1

x-3=1,x=4

x-3=-1,x=2

4.

x+1/x=3

平方得

x²+1/x²+2=9

x²+1/x²=7

x²/(x的4次方+x²+1)

=1/(x²+1/x²+1)

=1/(7+1)

=1/8