Which equation represents a line that passes through (4,1/3) and has a slope of 3/4?

Mathematics

2 answers:

velikii [3]3 years ago

3 0

We can use the point-slope equation:
$y = mx + b$
m, the slope, is 3/4:
$y = \frac{3}{4} x + b$
To find b, we plug in the point (4,1/3):
$( \frac{1}{3} ) = \frac{3}{4} (4) + b \\ \frac{1}{3} = 3 + b \\ \frac{1}{3} = \frac{9}{3} + b$
$- \frac{8}{3} = b$

Therefore, the point-slope equation is
$y = \frac{3}{4} x - \frac{8}{3}$

Now we have to see which answer matches.

$y - \frac{3}{4} = \frac{1}{3} (x - 4) \\ y - \frac{3}{4} = \frac{1}{3} x - \frac{4}{3} \\ y - \frac{9}{12} = \frac{1}{3} x - \frac{16}{12}$
$y = \frac{1}{3} x - \frac{7}{12}$
Since this is not the same, we try the next one.

$y - \frac{1}{3} = \frac{3}{4} (x - 4) \\ y - \frac{1}{3} = \frac{3}{4} x - 3 \\ y - \frac{1}{3} = \frac{3}{4} x - \frac{9}{3}$
$y = \frac{3}{4} x - \frac{8}{3}$

This is the same, so this is the answer. We should still double-check the other answers.

$y - \frac{1}{3} = 4(x - \frac{3}{4} ) \\ y - \frac{1}{3} = 4x - 3 \\ y - \frac{1}{3} = 4x - \frac{9}{3}$
$y = 4x - \frac{8}{3}$
This one is not equivalent.

$y - 4 = \frac{3}{4} (x - \frac{1}{3} ) \\ y - 4 = \frac{3}{4} x - \frac{1}{4} \\ y - \frac{16}{4} = \frac{3}{4} x - \frac{1}{4}$
$y = \frac{3}{4} x + \frac{15}{4}$
This one also does not work.

The answer is the second one:
$y - \frac{1}{3} = \frac{3}{4} (x - 4)$