Find the equation of the line through (0,-2) and (4, 18).

Mathematics

1 answer:

Montano1993 [528]2 years ago

3 0

Let me = slope

m = (18 - (-2))/(4 - 0)

m = 20/4

m = 5

We now plug slope 5 and one of the given points into the point-slope formula.

y - y_1 = m(x - x_1)

y - 18 = 5(x - 4)

y - 18 = 5x - 20

y = 5x - 20 + 18

y = 5x - 2

Done!

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telo118 [61]

Answer: the x-intercept is (-10,0), the y-intercept is (0,45/2)

Explanation:

First, we need to determine the function describing the line.

From the table, it is obvious that the y values increase by 9 every increase of 4 of the x values. So, the slope is 9/4 and the function looks like this:

$y = m x+ b = \frac{9}{4}x + b$

with the y-intercept (or bias) b still unknown. This can be determined by using one of the point from the table, like so:

$-18 = \frac{9}{4}\cdot 2+b\\\implies b = -18 -\frac{9}{2}=\frac{45}{2}\\y = \frac{9}{4}x+\frac{45}{2}$

The above function form makes it easy to read off the y-intercept, which is (0,45/2) or (0,22.5). The x-intercept is obtained by setting y = 0 and solving for x:

$y = \frac{9}{4}x+\frac{45}{2}\\0 = \frac{9}{4}x+\frac{45}{2}\\-\frac{45}{2}=\frac{9}{4}x\\x = -10$