Q: If the slope of the line through (-3,6) and (1,y) is 1/2, what is the value of y?
Explanation: Slope is computed by the formula (y2 – y1) / (x2 – x1) … the change in y divided by the change in x.
(y – 6) / (1 – -3) = 1 / 2
(y – 6) / 4 = 1 / 2
Multiply both sides by 4 and you have:
y – 6 = 2
y = 8
BUT, if you’re taking a test and having trouble remembering the method above, try this instead: Plot the point (-3,6) on a graph and move from that point with a slope of 1/2. Move up 1, right 2, up1, right 2… and repeat this pattern until your x-value is 1. Then, read the y-value at the same point. This is not my favorite way, but it works!
And one more thing! If this were a multiple choice question, you could use my TI-84 Plus program ‘DISTANCE’ (which finds distance, midpoint, and slope for any two ordered pairs). Substitute one of the answer choices for x, and see if the program reports that slope is 1/2.