Let the equation of the 2 lines l and k be
y = m1 * x + c1
y = m2 * x + c2
1 - Insufficient. Product of x intercepts = +ve.
We know that x intercept is the point at which y = 0
For line l: x = -c1 / m1
For line k: x = -c2 / m2
Product = c1c2 / m1m2 > 0
We can't infer that m1m2 > 0 since it depends on c1c2
2 - insufficient. Y intercept is -ve
For line l: y = c1
For line k: y = c2
Product = c1c2 < 0
We can't infer m1m2 from here
If we combine 1 and 2, we have c1c2 < 0 which implies that m1m2 < 0
(for c1c2/m1m2 > 0)
Hence C
I think I'm missing some datapoint here as I haven't made use of (4,3)
in the question stem...
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Product of slopes
Source: Beat The GMAT — Data Sufficiency |
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