WAEC Mathematics

If $M$ and $N$ are the points $(-3,8)$ and $(5,-7)$ respectively, find $MN$.

a.

8 units

b.

11 units

c.

15 units

d.

17 units

Correct answer: D

We are told to find the distance between points $M$ and $N$. The distance between two points $(x_1, y_1)$ and $(x_2, y_2)$ on the x-y plane is $\sqrt{(x_1-y_2)^2+(x_2-y_2)^2}$. The distance between the two points $M$ and $N$ will be

$\sqrt{(-3-5)^2+(8-(-7))^2}\\
= \sqrt{(-8)^2+(15)^2} \\
= \sqrt{64+225} = \sqrt{289} = 17$