Can I see the rest of the problem of number 18 please
The formula is y=mx+b
To get the slope or m, use this formula
(the second y minus the first y)/(the second x minus the first x)
Now set it up.
(10-7)/(2--1)
3/3=slope is 1.
y=1x+b
Insert one of the points for x and y.
i will do (-1,7)
7=1(-1)+b
7=-1+b
8=b
Insert this into the final equation:
y=1x+8
Try it out. If you're not sure, try both points. If it works, then you set it up correctly.
1st and 2nd pictures are for finding area and 3rd picture is for finding perimeter
hope you understood well and if not and you can ask again
the required ans is 3√b+b/3b