Mathematics
posted by Demetria .
The formula N = 2Xsquared + 22X + 320 represents the number of inmates, N, in thousands, in U.S. state and federal prisons x years after 1980. According to the formula, in what year were there 740 thousand inmates in the U.S. state and federal prisons?

The formula N = 2Xsquared + 22X + 320 represents the number of inmates, N, in thousands, in U.S. state and federal prisons x years after 1980. According to the formula, in what year were there 740 thousand inmates in the U.S. state and federal prisons?
2x^2 + 22x + 320 = 740
2x^2 + 22x  420 = 0
x^2 + 11x  210 = 0
(x  10)(x + 21)
10 years