Question

How do you find two values of x such that point (x, 5) is five units from the point (-1, 2)?

Answer 1

`x=3`
`x=-5`

Explanation:

The distance formula is
`d=sqrt((x_2-x_1)^2+(y_2-y_1)^2)`
`5=sqrt((-1-x)^2+(2-5)^2)`
`5=sqrt((x+1)^2+(-3)^2)`
`5=sqrt((x+1)^2+9)`
`25=(x+1)^2+9`
`16=(x+1)^2`
`+-4=x+1`

`x=3`
`x=-5`

A faster way to do this is to plot the point `(-1,2)` and use a
3-4-5 right triangle to find x where y=5.