Difference between revisions of "2004 AMC 12A Problems/Problem 5"

Problem

The graph of the line $y=mx+b$ is shown. Which of the following is true?

$\mathrm {(A)} mb<-1 \qquad \mathrm {(B)} -1 $01$

Solution

It looks like it has a slope of $-\dfrac{1}{2} (looking at the intercepts) and is shifted $0 up. Try $m=-\dfrac{1}{3}$ and $b=\dfrac{4}{5}$.

$\dfrac{4}{5}\cdot \dfrac{-1}{3}=\dfrac{-4}{15} \Rightarrow \mathrm {(B)}$