the value of y varies directly with x, and y= -14 when x = 1/2. find y when x = -1.

Answer 1

two ways to do this:

1.

"y varies directly with x " y = kx , where k is a constant
when x = 1/2, y = -14
-14= (1/2)k
k = -28
so y = -28x
if x = -1
y = -28(-1) = 28

2. Just use a ratio:
(1/2) / -14 = -1/y
1/2)y = 14
y = 28

notice the actual "calculation " is the same