Question Video: Evaluating Linear Functions Mathematics • 8th Grade

Evaluate 𝑓(βˆ’π‘₯), given that 𝑓(π‘₯) = 3π‘₯ + 7.

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Video Transcript

Evaluate 𝑓 of negative π‘₯, given that 𝑓 of π‘₯ is equal to three π‘₯ plus seven.

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

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

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