Find the value of the following expressions, when $x=-1$
$(i)$. $2x-7$
$(ii)$. $-x+2$
$(iii)$. $x^2+2x+ 1$
$(iv)$. $2x^2-x-2$

Given: 

$(i)$. $2x-7$

$(ii)$. $-x+2$

$(iii)$. $x^2+2x+ 1$

$(iv)$. $2x^2-x-2$

 To do: To find the value of the given expressions, when $x=-1$

Solution: 

$(i)$. $2x-1$

$=2\times\ (-1)-7$

$=-9$

$(ii)$. $-x+2$

$=-(-1)+2$

$=1+2$

$=3$

$(iii)$. $x^2+2x+1$

$=(-1)\ \times\ (-1)+2\ \times\ (-1)+1$

$=1-2+1$

$=0$

$(iv)$. $2x^2-x-2$

$=2(-1)\ \times\ (-1)-(-1)-2$

$=2+1-2=1$