The slope-intercept form of the equation of a line is

y = {\color{red}{m}}x+{\color{blue}{b}},

where {\color{red}{m}} is the slope of the line and {\color{blue}{b}} is the y -intercept.

To illustrate, consider the line y={\color{red}{2}}x+{\color{blue}{1}}, shown below.

Looking at the line, we notice that:

  • The slope of the line is m={\color{red}{2}}, because a change of 1 in the x -direction results in a change of 2 in the y -direction.

  • The y -intercept of the line, denoted b , is b={\color{blue}{1}}, because the line hits the y -axis at the point (0,{\color{blue}{1}}).

Note: The coordinates of the y -intercept are always (0,{\color{blue}{b}}).

Finally, if the slope m = 0 (i.e., we have a horizontal line), the slope-intercept form must be y=0x+{\color{blue}b}, which reduces to y={\color{blue}b}.

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What are the slope and y -intercept of the line y=2x-9?

EXPLANATION

The equation is in slope-intercept form y={\color{red}{m}}x+{\color{blue}{b}}, where \color{red}{m} is the slope and \color{blue}{b} is the y -intercept.

For the equation y=2x-9, we see that the slope is {\color{red}{m=2}} and the y -intercept is {\color{blue}{b=-9}}.

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Determine the slope and $y$-intercept of the line $y=4x-3.$

a
b
c
d
e

What are the coordinates of the point where the line $y = -9x + 17$ intersects the $y$-axis?

a
$(0,-9)$
b
$(0,-17)$
c
$\left(0,-\dfrac{9}{17}\right)$
d
$(0,17)$
e
$\left(0,\dfrac{17}{9}\right)$

What are the slope and $y$-intercept of the line $y = 3?$

a
The slope is $0$ and the $y$-intercept is $3$
b
The slope is $-1$ and the $y$-intercept is $1$
c
The slope is $3$ and the $y$-intercept is $0$
d
The slope is $0$ and the $y$-intercept is $1$
e
The slope is $0$ and the $y$-intercept is $-3$

The line shown above passes through the points (0,-2) and (2,2).

EXPLANATION

We will write the equation of the line in the slope-intercept form y=mx+b. So, we need to work out the slope m and the y -intercept b.

From the graph, we see that the line intercepts the y -axis at (0,-2). So, the y -intercept is b = -2.

We can calculate the slope of the line by choosing two points on the line and applying the slope formula. The line passes through the points (0,-2) and (2,2), so we calculate its slope as follows: \begin{align*} m &= \dfrac{y_2-y_1}{x_2-x_1} \\[5pt] &= \dfrac{2 - (-2)}{2 - 0} \\[5pt] &= \dfrac{4}{2} \\[5pt] &= 2 \end{align*}

Substituting the slope m = 2 and the y -intercept b = -2 into the slope-intercept form y = mx + b, we obtain the equation of the line: y = 2x - 2.

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Given that the slope of the line shown above is $2,$ what is the equation of the line?

a
$y+2x=0$
b
$y=2x-3$
c
$y=2x+3$
d
$y=2x+1$
e
$y=3x+2$

The line shown above passes through the points $(0,1)$ and $(1,3).$ What is the equation of the line?

a
$y=2x-1$
b
$y=2x+1$
c
$y=x+1$
d
$y=x-1$
e
$y=3x+1$

Consider the line shown above, which has a slope of $\dfrac23.$ The equation of the line is $y=$

a
b
c
d
e

Find the equation of the line shown below.

EXPLANATION

We will write the equation of the line in the slope-intercept form y=mx+b. So, we need to work out the slope m and the y -intercept b.

From the graph, we see that the line intercepts the y -axis at (0,2). So, the y -intercept is b=2.

We can calculate the slope of the line by choosing two points on the line and applying the slope formula. The line passes through the points (0,2) and (6,0), so we calculate its slope as follows: \begin{align*} m &= \dfrac{y_2-y_1}{x_2-x_1} \\[5pt] &= \dfrac{0-2}{6-0} \\[5pt] &= \dfrac{-2}{6} \\[5pt] &= -\dfrac{1}{3} \end{align*}

Substituting the slope m=-\dfrac{1}{3} and the y -intercept b=2 into the slope-intercept form y=mx+b, we obtain the equation of the line:

y=-\dfrac{1}{3}x+2

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Given that the slope of the line shown above is $-2,$ what is the equation of the line?

a
$y=-2x-2$
b
$y=-x-1$
c
$y=-2x-1$
d
$y=-2x+2$
e
$y=2x+2$

The line shown above passes through the points $(0,5)$ and $(5,0).$ What is the equation of the line?

a
$y=-5x+5$
b
$y=5x+5$
c
$y=-x - 5$
d
$y=-x+5$
e
$y=-5x-5$

Calculate the equation of the straight line that passes through the points (0,8) and (3,2).

EXPLANATION

We will write the equation of the line in the slope-intercept form y=mx+b. So, we need to work out the slope m and the y -intercept b.

First, we calculate the slope m using the given points: \begin{align} m &= \frac{y_2 - y_1}{x_2 - x_1} \\[5pt] &=\frac{2 - 8}{3 - 0} \\[5pt] &=\frac{-6}{3} \\[5pt] &=-2 \end{align}

The coordinates of the y -intercept are always (0,{\color{blue}{b}}). We know that the line passes through the point (0,{\color{blue}{8}}), so the y -intercept is b={\color{blue}{8}}.

Substituting the slope m=-2 and the y -intercept b=8 into the slope-intercept formula y=mx+b, we reach

y=-2x+8.

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Find the equation of the line that passes through the points $(0,10)$ and $(4,26).$

a
$y=4x+10$
b
$y=2x+10$
c
$y=3x+26$
d
$y=4x+26$
e
$y=3x+10$

Find the equation of the line that passes through the points $(8,7)$ and $(0,31).$

a
$y=-2x+7$
b
$y=3x+31$
c
$y=-2x+31$
d
$y=-3x+7$
e
$y=-3x+31$

Written in the form $y=mx+b,$ what is the equation of the line that passes through the points $(3,-10)$ and $(0,-4)?$

a
b
c
d
e
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