The midpoint of the line segment  AB has coordinates of $\left(1,-2\right);$ if  $A\text{'}s$  coordinates are (-3,2) then B's coordinates are:

To answer this question, we will use the midpoint formula.  And it is written as $x=\frac{x_1+x_2}{2},y=\frac{y_1+y_2}{2}$where $\left(x_1,y_1\right),\left(x_2,y_2\right)$are the two given points and (x,y) is the coordinate of the midpoint of the line segment connecting $\left(x_1,y_1\right),\left(x_2,y_2\right)$

Given that, the coordinates of the midpoint of line segment AB are $(1,-2)$

 Also, coordinates of A are $(-3,2)$.

Let the coordinates of B be (a, b)

Midpoint of two points $\left(x_1,y_1\right)$and $\left(x_2,y_2\right)$ is calculated by the formula $\left(\frac{x_1+x_2}{2},\frac{y_1+y_2}{2}\right)$

Hence, midpoint of $AB=\left(\frac{-3+a}{2},\frac{2+b}{2}\right)=(1,-2)$

$=\frac{-3+a}{2}=1; \frac{2+b}{2}=-2$

$=-3+\mathrm{a}=2; 2+\mathrm{b}=-4$

$\therefore a=5;b=-6$

Hence, the coordinates of B are $(5,-6)$.