Question

Write the equation of the line that crosses (-13, -7) and has a slope of zero.

A) y = -7
B) x = -13
C) y = -7x
D) y = 0

Answer 1

Our answer is y = -7.

`\Large\texttt{Explanation}`

We are asked to find the equation of a line that:

• crosses the point (-13,-7)
• has a slope of 0

When a line has a slope of 0, it has the form y = the y-coordinate of the point it crosses (-7).

So, the line is y = -7.

Alternatively, we could use the point-slope formula:

`\bf{y-y_1=m(x-x_1)}`

Plug in the values -

`\bf{y-(-7)=0(x-(-13)}`

`\bf{y+7=0(x+13)}`

`\bf{y+7=0}`

`\bf{y=-7}`

`\therefore` y = -7

Answer 2

A) y = -7

Explanation:

A slope of zero means that the value of y is independent on x.

y = mx + b, where m is the slope. For slope of zero:

y = 0*x + b, or

y = b

b is the y-intercept, the value of y when x = 0. Since y = b, no matter the value of x, we can say that b = -7

The equation of the line that crosses (-13,-7) and has a slope of zero is:

y = -7