Question

What is a reason that we need to be able to use the quadratic formula rather than solving all quadratic equations by graphing?

Answer 1

Here are some examples of how the Quadratic Formula works:

Solve x2 + 3x – 4 = 0

This quadratic happens to factor:

x2 + 3x – 4 = (x + 4)(x – 1) = 0

.

Then, as expected, the solution is x = –4, x = 1.