SAT Mathematics Practice Test 2

In the xy−plane, the slope m of the line that passes through the points (x1,y1) and (x2,y2) is given by the formula m=

y2−y1

x2−x1

Thus, if the graph of the linear function f has intercepts at (a,0) and (0,b), then the slope of the line that is the graph of y=f(x) is m=

0−b

a−0

=−

b

a

It is given that a + b = 0, and so a = −b. Finally, substituting −b for a in m = −b/a gives m=−

b

−b

=1, which is positive.
Choices B, C, and D are incorrect and may result from a conceptual misunderstanding or a calculation error.