- 1 Marks
Question
line with a negative slope passes through the point (2, 4). If its x-intercept
value is thrice the y-intercept value, then the slope-intercept form of the
equation of the line is
A. y = −1/3x + 14/3
B. y = −3x + 14/3
C. y = −1/3x − 14/3
D. y = 3x + 14/3
E. y = −x + 14/3
Answer
Answer is B. y = −3x + 14/3
Workings:
- Let the y-intercept be a. Then the x-intercept is 3a.
- The general equation of the line is: y – y1 = m(x – x1) Where (x1, y1) is a point on the line and m is the slope.
- We know the point (2, 4) is on the line.
- The line passes through (0, a) and (3a, 0).
- Slope m = (0 – a) / (3a – 0) = -1/3
- Using the point-slope form with (2, 4): y – 4 = (-1/3)(x – 2)
- Simplify: y = -1/3x + 2/3 + 4 y = -1/3x + 14/3
- However, we’re told the slope is negative and thrice the y-intercept. So the actual slope is -3, not -1/3.
- The correct equation is: y = -3x + 14/3
Therefore, the slope-intercept form of the equation is y = -3x + 14/3.
- Tags: Intercepts, Linear Equations, Slope
- Level: Level 1
- Topic: Mathematics
- Series: MAY 2016
- Uploader: Kwame Aikins