Question

Find the value of B - A if the graph of Ax + By = 3 passes through the point (-7,2), and is parallel to the graph of x + 3y = -5.

Answer 1

B - A = 2

Explanation:

Recall that parallel lines have the same slope. Thus, line Ax + By = 3, parallel to x + 3y = -5, has the form x + 3y = C. This latter line passes through the point (-7, 2), and so -7 + 3(2) = C must be true. Then -7 + 6 = C, and C = -1.

In both equations A = 1 and B = 3. Thus, B - A = 3 - 1, or B - A = 2