Question

Show that the equation x^3 + x - 3 = 0 has a solution between 1 and 2

Answer 1

When x = 1:

1³ + 1 - 3 = -1

When x = 2:

2³ + 2 - 3 = 7

Since f(x) = x³ + x - 3 is continuous, it follows from the intermediate value theorem that for some c in the interval (1, 2), we have f(c) = 0, since f(1) < 0 < f(2).