If y varies directly as x and y=15 when x =5, what is the value of y when x = 15?
1 answer:
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First, you need to find the slope of the line. You can use this with the slope formula, 
, where the x's and y's are the given coordinates.
Plug in the coordinates
Subtract
Divide
-3
Now, plug the slope (m) and one pair of coordinates, I'll use (-2, 11), into point-slope form,
.
Plug in the values
y - 11 = -3 (x - (-2) Cancel out the double negative
y - 11 = -3 (x + 2)
-3
Now, plug the slope (m) and one pair of coordinates, I'll use (-2, 11), into point-slope form,
y - 11 = -3 (x - (-2) Cancel out the double negative
y - 11 = -3 (x + 2)