Maths Olympiad Prep

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, 2023

Algebra Difficulty 2.5 Junior Find the answer Canada

A line with a slope of 22 and
a line with a slope of 4-4 each have
a yy-intercept of 6. The distance
between the xx-intercepts of these
lines is

Pick one

Solution

The line with a slope of 2 and yy-intercept 6 has equation y=2x+6y = 2x + 6.

To find its xx-intercept, we set
y=0y = 0 to obtain 0=2x+60 = 2x + 6 or 2x=62x = -6, which gives x=3x = -3.

The line with a slope of 4-4 and
yy-intercept 6 has equation y=4x+6y = -4x + 6.

To find its xx-intercept, we set
y=0y = 0 to obtain 0=4x+60 = -4x + 6 or 4x=64x = 6, which gives x=64=32x = \frac{6}{4} = \frac{3}{2}.

The distance between the points on the xx-axis with coordinates (3,0)(-3,0) and (32,0)(\frac{3}{2},0) is 3+323 + \frac{3}{2} which equals 62+32\frac{6}{2} + \frac{3}{2} or 92\frac{9}{2}.

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Source: CEMC, University of Waterloo, licensed CC-BY-NC-4.0. Statement reproduced verbatim; metadata (topic, difficulty) added by this project.