SOLUTION: I have a problem help Find the value for A so that the given pair of lines will be parallel -7x + 8y = 13 Ax + 4y = 15 find the value for A so that the given pair of lines will

Question 83770This question is from textbook plato interactive mathematics
: I have a problem help
Find the value for A so that the given pair of lines will be parallel
-7x + 8y = 13
Ax + 4y = 15
find the value for A so that the given pair of lines will be perpendicular
20x + 5y = 18
Ax +17y = 9 This question is from textbook plato interactive mathematics

Answer by Earlsdon(6294) (Show Source): You can put this solution on YOUR website!
1)
Remember that parallel lines have identical slopes.
The first thing you ought to do is put your equations into the slope-intercept form:
y = mx + b where m is the slope and b is the y-intercept.
Add 7x to both sides.
Now divide both sides by 8.
Here, you can see that the slope,
Subtract Ax from both sides.
Now divide both sides by 4.
Here, you can see that the slope,
So, if you set these two slope equal to each other, you can solve for A.
Multiply both sides by -4.

2)
Remember that perpendicular lines have slopes that are the negative reciprocal of each other.
Subtract 20x from both sides.
Now divide both sides by 5.
Here, the slope is
Subtract Ax from both sides.
Now divide both sides by 17.
Here, the slope,
Now you want to set one of the slopes equal to the negative reciprocal of the other.
Simplify and solve for A. Multiply both sides by -17.

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