A family of linear functions is given by f(x) = mx + (3-2 m) where x is the independent variable and m is a constant.
a) Graph / for m = 0, 1, 2, -3 and -5
b) What do all the graphs in part a) have in common?
c) Justify your answer to part b) analytically. d) Write the equation of the family of functions whose graphs pass by the same point (-2,-4).
Answers & Comments
Answer:
a) To graph f(x) = mx + (3-2m), we need to substitute different values of m and plot the resulting graphs.
For m = 0, f(x) = 0x + (3-2 * 0) = 3
For m = 1, f(x) = 1x + (3-2 * 1) = 1x + 1
For m = 2, f(x) = 2x + (3-2 * 2) = 2x - 1
For m = -3, f(x) = -3x + (3-2 * -3) = -3x + 9
For m = -5, f(x) = -5x + (3-2 * -5) = -5x + 23
b) All the graphs in part a) have the common characteristic of having the same slope, but different y-intercepts.
c) Analytically, this can be proven by noting that the slope of all the graphs is m, and the y-intercept of each graph is (3-2m), which is different for each value of m. The slope and y-intercept of a linear function completely determine its graph.
d) The equation of the family of functions whose graphs pass by the same point (-2,-4) can be found by solving for m. Let's say f(x) = mx + (b-2m). We know that when x = -2, the function must equal -4, so we can write an equation using this information:
-4 = m * (-2) + (b - 2 * m)
Expanding and solving for m and b, we get:
-4 = -2m + b
-2m = -4 - b
-2m = -4 - b
m = 2 + b/2
Substituting m back into f(x) = mx + (b-2m), we get:
f(x) = (2 + b/2) x + (b - 2 * (2 + b/2))
f(x) = 2x + b/2 + b - 2 * 2 - 2 * b/2
f(x) = 2x - 4