Question Video: Evaluating Linear Functions Mathematics • 8th Grade

Video Transcript

Evaluate 𝑓 of negative 𝑥, given that 𝑓 of 𝑥 is equal to three 𝑥 plus seven.

In this question, we’re given the linear function 𝑓 of 𝑥 is equal to three 𝑥 plus seven. In order to evaluate 𝑓 of negative 𝑥, we need to substitute negative 𝑥 for 𝑥 in our function. This gives us three multiplied by negative 𝑥 plus seven. Multiplying a positive by a negative gives a negative answer. So, three multiplied by negative 𝑥 is negative three 𝑥. This means that 𝑓 of negative 𝑥 is negative three 𝑥 plus seven.

If 𝑓 of 𝑥 is equal to three 𝑥 plus seven, then 𝑓 of negative 𝑥 is negative three 𝑥 plus seven. The coefficient of 𝑥 has changed from a positive to a negative.