The equation of a straight line
Answers are for parents and teachers.
1
Find the slope, x-intercept and y-intercept of 5x + 2y = 20.
Slope −5/2, x-intercept 4, y-intercept 10.
2
Write the line through (−1, 4) and (2, −2) in the form y = mx + b.
m = −6/3 = −2; y − 4 = −2(x + 1), y = −2x + 2.
3
Write the line through (2, 3) parallel to y = 4x − 1, and the one perpendicular to it.
Parallel: y − 3 = 4(x − 2), y = 4x − 5. Perpendicular: y − 3 = −(x − 2)/4, y = −x/4 + 3.5.
4
A water tank holds 200 litres and loses 8 litres each minute. Write the volume y after x minutes and find when it is empty.
y = 200 − 8x; empty when x = 25 minutes.
5
A taxi costs 8 LE to start and 3 LE per km. A trip cost 35 LE. How many km?
3x + 8 = 35, x = 9 km.