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What is the X intercept of non horizontal line m?

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Source: — Data Sufficiency |

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by Ian Stewart » Sat Jun 29, 2019 5:06 am
Our line has an equation y = mx + b, where m is the slope, b the y-intercept.

To find the x-intercept of a line, we find the value of x when y=0. If we plug in y=0 here, we find

0 = mx + b
x = -b/m

Statement 1 tells us m = 4b, and if we substitute that for m above, we learn that x = -b/(4b) = -1/4, so we can find the x-intercept and Statement 1 is sufficient.

Statement 2 is clearly not sufficient, because all we know is the y-intercept of the line, so the x-intercept could be anything.
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