What is m if f(x) = m x and f(7) = 21?

What is m if f(x) = m x and f(7) = 21?

• A. 3
• B. 7
• C. 21
• D. 14

Answer: (A)

In a function of the form f(x) = m x, the number m is the factor that scales x—the rate of change or slope of this linear relation. You’re told f(7) = 21, so plug in x = 7: f(7) = m × 7 = 21. Solve for m by dividing both sides by 7, giving m = 21/7 = 3. Check: if m = 3, then f(7) = 3 × 7 = 21, which matches the given value. Choosing any other value for m would yield a different result when x = 7, so they wouldn’t fit the condition.

In a function of the form f(x) = m x, the number m is the factor that scales x—the rate of change or slope of this linear relation. You’re told f(7) = 21, so plug in x = 7: f(7) = m × 7 = 21. Solve for m by dividing both sides by 7, giving m = 21/7 = 3.

Check: if m = 3, then f(7) = 3 × 7 = 21, which matches the given value. Choosing any other value for m would yield a different result when x = 7, so they wouldn’t fit the condition.