Giúp e với mấy anh chị ơi

Đáp án:

`a)` `lim_{x->-1}(x^2-8x-9)/(x+1)`$\\$ `=lim_{x->-1}((x+1)(x-9))/(x+1)`$\\$ `=lim_{x->-1}(x-9)`$\\$`=-1-9`$\\$`=-10`

`-------`

`b)` `lim_{x->2}(x-sqrt(3x-2))/(2-x)`$\\$ `=lim_{x->2}(x^2-3x+2)/((2-x).(x+sqrt(3x-2))`$\\$ `=lim_{x->2}((x-1)(x-2))/(-(x-2).(x+sqrt(3x-2))`$\\$ `=lim_{x->2}(x-1)/(-(x+sqrt(3x-2))`$\\$ `=(2-1)/(-(2+sqrt(3.2-2))`$\\$`=-1/4`

`---------`

`c)` `lim_{x->1^+}(x+1)/(1-x)`$\\$ `=lim_{x->1^+}[(x+1).(1)/(1-x)]`$\\$`=-oo`

Vì `{(lim_{x->1^+}(x+1)=1+1=2>0),(),(lim_{x->1^+}(1)/(1-x)=-oo):}`

`---------`

`d)` `lim_{x->-oo}(x^4+2x^2-1)`$\\$ `=lim_{x->-oo}[x^4.(1+2/x^2-1/x^4)]`$\\$`=+oo`

Vì `{(lim_{x->-oo}x^4=+oo),(),(lim_{x->-oo}(1+2/x^2-1/x^4)=1>0):}`