Question

between which two ordered pairs does the graph of f(x) = x2 + x – 9 cross the negative x-axis? quadratic formula: x = (–6, 0) and (–5, 0) (–4, 0) and (–3, 0) (–3, 0) and (–2, 0) (–2, 0) and (–1, 0)

Answer 1

i just took the test the answer is A (-6,0) and (-5,0)

Answer 2

The negative root of x^2+x-9=0 is -1/2 - (√37) / 2 ≈ -3.541, so the answer is:

between (–4, 0) and (–3, 0).

If you don't want to calculate the roots, you can verify that the x-axis is crossed between x=-4 and x=-3 by observing the sign of f change.

f(-4) = 16-4-9 = 3
f(-3) = 9-3-9 = -3

The sign changed (f went from 3 to -3) so it must have crossed the x-axis.