數學專家請快進!!!

1)(x+y+z)(x+y-z)
=x(x+y-z)+y(x+y-z)+z(x+y-z)
=x^2+xy-xz+xy+y^2-yz+xz+yz-z^2
=x^2+2xy+y^2-z^2
2)16p^2+48pq+36q^2
=4(4p^2+12pq+9q^2)
=4((2p)^2+2(2p)(3q)+(3q)^2)
=4(2p+3q)^2
3)6xy+18xz/8yz+24z^2
=6x(y+3z)/8z(y+3z)
=6x/8z
=3x/4z
4)x/x^2+2x-1/x-2
=x/x(x+2)-1/x-2
=1/(x+2)-1/(x-2)
=(x-2)-(x+2)/(x+2)(x-2)
=-4/(x+2)(x-2)
5.2a+b=4------(1)
a-2b=7------(2)
(2)*2,
2a-4b=14------(3)
(1)-(3),
(2a+b)-(2a-4b)=4-14
5b=-10
b=-2
sub b=-2 into (2)
a-2(-2)=7
a+4=7
a=3
therefore a=3,b=-2

1）
X（X＋Y﹣Z）＋Y（X＋Y﹣Z）＋Z（X＋Y﹣Z）
自已乘埋入去

2）
(4P)^2+2(4)(6)+(6Q)^2
=(4P+6Q)^2
3

6X(Y＋3Z） ／8Z（Y＋3Z）
＝3X／4Z

4.X/x(x+2) - 1/x-2
=<x(x-2)-x(x+2)> /x(x^2-4)
=-4x/x(x^2-4)
5
a=7+2b

2(7+2b)+b=4
b=-2
when b=-2 a=3