(a) Deduce the equation of a line whose slope is of 1.7 and which passes through the point (2, 5).
(b) Plot the graph of the line.
(a) Using equation (2.9), the equation of the line is deduced as
y − y_1 = m(x − x_1)
y − 5 = 1.7(x − 2)
y − 5 = 1.7x − 3.4
y = 1.6 + 1.7x
This line has a slope of 1.7 and it intersects the y-axis at y = 1.6.
(b) To plot the line it is necessary to calculate at least two points on the line; however, it is a good idea to calculate three points in case of error. All three points should lie exactly on the line. Using method A, take suitable x-values and calculate the corresponding y-coordinates from the equation of the line as shown in Table 2.8. These points are plotted in Figure 2.28.
Table 2.8 Calculating points on the line, y = 1.6 + 1.7x | ||
x | y= 1.6 + 1.7x | Point (x, y) |
-2 | y = 1.6 + 1.7(−2)=−1.8 | (−2, −1.8) |
0 | y = 1.6 + 1.7(0) = 1.6 | (0, 1.6) |
2 | y = 1.6 + 1.7(2) = 5 | (2, 5) |