Find the value of x.

Question

The area of a rectangle = 105
The length is 2x+1
Width is x
__________________________________

I tried solving it :
Arec = l x w
105 = (2x+1)x
105 = 2x^2 + x
0= 2x^2 + x - 105

This is where I get stuck on...

Answer 1

quadratic equation
x = [ -1 +/- sqrt (1+840)]/4
= [ -1 +/- 29 ]/4
= 28/4 forget negative solution
= 7

or
(x - 7) (2x + 15) = 0