The line passing threw (- 1,y) and (1,0) is perpendicular to the lines joining ( 2,3) and (-2,1) find y

The slope of a line is found by taking the difference in y divided by the difference in x. For the point they give us that's
(3-1)/(2-(-2)) = 2/4 = 1/2
A line will be perpendicular to another line if their slopes are negative reciprocals of each other. So we want a line whose slope is -2.
Setting up the slope equation with the y in place gives
(0-y)/(1-(-1)) = (-y)/2
We need this to equal -2
-y/2=-2
-y = -4
y = 4

A=bxh3.2x1.8=5.76 centimeters square