A = lw
80 = 2x(x - 3)
80 = 2x(x) - 2x(3)
80 = 2x² - 6x
0 = 2x² - 6x - 80
0 = 2(x²) - 2(3x) - 2(40)
0 = 2(x² - 3x - 40)
2 2
0 = x² - 3x - 40
0 = x² - 8x + 5x - 40
0 = x(x) - x(8) + 5(x) - 5(8)
0 = x(x - 8) + 5(x + 8)
0 = (x + 5)(x + 8)
0 = x + 5 or 0 = x + 8
- 5 - 5 - 8 - 8
-5 = x or -8 = x
The values of x are -5 and -8.
