`12/(-17)-8/16`

`=-12/17-1/2`

`=-24/34 -17/34`

`=-41/34`

`2/7-(-3)/11+5/7-1/(-4)-6/11`

`=2/7+3/11+5/7+1/4-6/11`

`=(2/7+5/7)+(3/11-6/11)+1/4`

`=7/7-3/11+1/4`

`=1-3/11+1/4`

`=44/44-12/44+11/44`

`=43/44`

`bb(\text{A feww weeks ago,she watched TV while she had breakfast)`

`(x^2 -x)^2 +x=x^2 +30`

`<=>(x^2 -x)^2 -(x^2 -x)-30=0`

Đặt `t=x^2 -x`

`t^2 -t-30=0`

`<=>t^2 -6t+5t-30=0`

`<=>t(t-6)+5(t-6)=0`

`<=>(t-6)(t+5)=0`

`<=>[(t-6=0),(t+5=0):}`

`<=>[(x^2 -x-6=0),(x^2 -x+5=0):}`

`<=>x^2 -x-6=0`

`<=>x^2 -3x+2x-6=0`

`<=>x(x-3)+2(x-3)=0`

`<=>(x-3)(x+2)=0`

`<=>[(x-3=0),(x+2=0):}`

`<=>[(x=3),(x=-2):}`

Vậy `S={-2;3}`