x^2 + 15x + x + 10 = 90

I've been trying to get it for hours, I got -12, 20 which I think, well pretty much know are wrong. It IS for homework, but I am not posting this to cheat and plus this is only half of the question, I need to plug it in and find the measures of the angles. Thanks! Please solve for x, and give an explanation please!

## Answers (2)

x^2 + 15x + x = 90-10 moved the 10 to the otherside

x^2 + 15x + x =80

x(x+15+1)=80 factorize

x(x+16)=80

and then just by looking at it x= 4

4(4+15+1)=80

4(20)=80

80=80

the proper equation to factor is x^2 + 16x - 80 = 0 ... and 20 - 4 = 16 and 20*-4 = -80

although given the round numbers, I quickly guessed 4 also.

Reference:my brain, and experience