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?

1 answer

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