數學問題(急急急急急急........)

3r+4s-2r+7s
=3r-2r+4s+7s
=r+11s
4x2-2x+7-2x+3x2+5x-2
=4x2+3x2-2x-2x+5x+7-2
=7x2+x+5
a+2b+3c+4a-6b-2c
=a+4a+2b-6b+3c-2c
=5a-4b+c
2xy+3x-2y+4x-6y+ 5xy
=4x+3x+2xy+ 5xy-2y-6y
=7x+7xy-8y
4x+2xy/3y
=4x+2x/3
={(4x)3+2x}/3
=(12x+2x)/3
=14x/3
(x+1)/y+(y+1)/x
={(x+1)x+(y+1)y}/xy
=(x2+x+y2+y)/xy [[optional]]

9a)3r+4s-2r+7s
=3r-2r+4s+7s
=r+10s
b)4x的2次方-2x+7-2x+3x的2次方+5x-2
=4x的2次方+3x的2次方-2x+5x+3x-2
=7x的2次方+7x-2
c)a+2b+3c+4a-6b-2c
=a+4a+2b-6b+3c-2c
=5a-4b+c
d)2xy+3x-2y+4x-6y+5xy
=2xy+5xy+3x+4x-2y-6y
=7xy+7x-8y

a.) 4x+3y分之2xy
= 4x+3分之2x
=3分之14x
b.)y分之x+1+x分之y+1
=xy分之x2次方+x+y2次方+y