f(n) = 1/2n² - 10
h(t) = (5 - 2t)/(t - 1)
h(0.5) = (5 - 2(0.5))/(0.5-1) = 4/-8 = -0.5
f(-0.5) = 1/2(-0.5²) - 10 = 0.125 - 10 = -9.875 = -79/8
