Question Video: Evaluating Quadratic Functions Mathematics

Video Transcript

If 𝑓 of 𝑥 is equal to negative eight 𝑥 squared minus three 𝑥 plus four, find 𝑓 of negative three.

We’re asked to find the value of 𝑓 of negative three. And we recall that this is function notation for the value of 𝑓 of 𝑥 when 𝑥 is equal to negative three. This means in our function 𝑓 of 𝑥, wherever we have an 𝑥, we substitute negative three. So, we have 𝑓 of negative three is equal to negative eight times negative three squared minus three times negative three plus four. That is negative eight times nine plus nine plus four, which evaluates to negative 59. Hence, 𝑓 of negative three is equal to negative 59.