If f(x) = -2x + 7, find f(4).
Note
Substitute x = 4 into the function: f(4) = -2 × 4 + 7 = -1. A function gives an output for each input. To evaluate f(x), replace every x in the rule with the given number before simplifying. Be especially careful with negative inputs, because multiplying two negative signs can make a positive result. The correct answer is -1, which matches the calculation or reasoning shown.
