Question

How do you solve `x^ { 2} + 10x = 15`?

Answer 1

`x=-5+-2sqrt10`

Explanation:

`x^2+10x=15`
`x^2+10x-15=0`

Apply factoring (what multiplies to -15 and adds up to 10?)
if no answer, then proceed to quadratic equation

`x=(-b+-sqrt(b^2-4ac))/(2a)`
`x=(-10+-sqrt(10^2-4*1*-15))/(2*1)`
`x=(-10+-sqrt160)/(2)`
`x=(-10+-4sqrt10)/(2)`
`x=-5+-2sqrt10`

It's long at first, but after a while, you'll get the hang of it and you can do it in your head