TestPrep Geometry

[email protected] wrote:Is it okay to look at this questions as follow...

y = mx + b

After statement one we know:

3m = y - b

After statement two we know:

0 = -1/3m +b

Even with both statements, we are left with three equations and four unknowns, not enough to solve??

No, that's not correct. We want the y-intercept; in other words we want to find the point on the line when x = 0. So x is known in advance. Also, the y-coordinate we are looking for is b, so we only have two unknowns here: m and b. The problem is that the two statements give us the same equation, so while we appear at first to have two equations, two unknowns, we really only have one equation, two unknowns. You haven't translated the statements correctly into equations:

(1)The slope of line l is 3 times the y intercept

This tells you m = 3b

(2)The x intercept of line l is -1/3

This tells you that (-1/3, 0) is on the line, i.e. that 0 = m*(-1/3) + b. You can rearrange this, and it just says that m = 3b, exactly what we found from (1).