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Question 172485This question is from textbook Prentice Hall Mathematics ALGEBRA 1
: How do you write an equation in slope-intercept form for a line that passes through (0,2) and is perpendicular to x= -7?
This question is from textbook Prentice Hall Mathematics ALGEBRA 1
Answer by vleith(2983)   (Show Source):
You can put this solution on YOUR website! perpendicular lines have slopes that are negative reciprocals of each other. So what is the slope of the line  ? That line is a vertical line. It's slope is undefined. However, you know that a horizontal line is perpendicular to a vertical one.
What is the slope of a horizontal line? 0
So you have a point (0,2) and a slope of 0
That means we are looking for a horizontal line that runs thru the point (0,2).
We already know that m = 0
The general formula for that line is
You can do a more general look this way:
| Solved by pluggable solver: FIND a line by slope and one point |
What we know about the line whose equation we are trying to find out:
- it goes through point (0, 2)
- it has a slope of 0
First, let's draw a diagram of the coordinate system with point (0, 2) plotted with a little blue dot:
Write this down: the formula for the equation, given point  and intercept a, is
 (see a paragraph below explaining why this formula is correct)
Given that a=0, and  , we have the equation of the line:
Explanation: Why did we use formula  ? Explanation goes here. We are trying to find equation y=ax+b. The value of slope (a) is already given to us. We need to find b. If a point ( ,  ) lies on the line, it means that it satisfies the equation of the line. So, our equation holds for (, ):  Here, we know a, , and , and do not know b. It is easy to find out:  . So, then, the equation of the line is:  .
Here's the graph:
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