Question

If f(x) varies directly with x and f(x)=50 when x=–10, then what is f(x) when

x=15?
a) -150
b) -75
c) -30
d) -5

Answer 1

To find the value of f(x) when x = 15 in a direct variation, substitute the given values into the equation f(x) = kx. The correct answer is -75.

Step-by-step explanation:

To find the value of f(x) when x = 15, we can use the concept of direct variation. In direct variation, the relationship between two variables can be represented by the equation f(x) = kx, where k is the constant of variation. Given that f(x) = 50 when x = -10, we can substitute these values into the equation to find the value of k.

50 = k(-10)

Solving for k, we get k = -5. Now, we can substitute the value of x = 15 into the equation to find the value of f(x):

f(15) = -5(15) = -75

Therefore, f(x) = -75 when x = 15. So the correct answer is option b) -75.