How do I write an equation for:
A line parallel to x + 2y = 6, through (8,3)
A line perpendicular to x + 2y = 6 through (8,3)
Please explain! I really don't understand this concept. Thank you.
Update:Thanks to everyone's help! I finally understand this problem thanks to you guys :)
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Parallel:
2y=6-x
y=3-(1/2)x
y=-(1/2)x +c
3=-(1/2)(8)+c
c=7
So here is the equation: y=(-1/2)x +7
Perpendicular : You'll do the same for perp line, except the slope are opposite. y=(1/2)x+7
1) Rewrite the equation you have been given into x=mx + b format. In that form, m = slope and b = y-intercept.
x + 2y = 6
2y = -x + 6
y = (-1/2)x + 3
So, looking at the above, you can see that m = -1/2, so that is your slope.
A line that is parallel will have the same slope, so you know for the line you are trying to find, m = -1/2.
Use the following formula to find the equation of the line:
y - y1 = m(x - x1)
where m is the slope and x1 and y1 are a point (x1, y1) on the line (any point on the line that you know).
For this problem:
m = -1/2
(x1, y1) = (8,3)
Plug in the above values:
y - 3 = (-1/2)(x-8)
y - 3 = (-1/2)x - (-1/2)8
y - 3 = (-1/2)x + 4
y = (-1/2)x + 7
If you need to rearrange it into the same format as the equations in the question, do the following:
y = (-1/2)x + 7
(1/2)x + y = 7
2) Since we are using the same equation, we already know the slope of x+2y=6 is -1/2.
When a line is perpendicular to another, its slope will be the negative reciprocal of the other slope.
This means, to find the slope of the new line:
a) flip the fraction (eg: from 1/3 to 3/1)
b) switch signs (from positive to negative, or from negative to positive)
The first line's slope is -1/2.
The negative reciprocal is 2.
So, as in the first question, use the following formula and plug in your slope (m=2) and the point (8,3) to find the equation.
y - y1 = m(x - x1)
y - 3 = 2(x - 8)
y - 3 = 2x - 16
y = 2x - 13
I hope this helped!
PARALLEL
First find the slope
x + 2y = 6, passing through (8,3)
2y= -x+6 rewrite the equation into y=mx+b
divide both sides by 2
y= -1x/2+3
m= -1/2 and parallel lines have the same slope.
Second find b by substituting the 2 points given
x=8
y=3
3= -1/2(8)+b then solve
7=b
1st equation: y= -1x/2+7
PERPENDICULAR
x + 2y = 6, passing through (8,3)
2y= -x+6 rewrite the equation into y=mx+b
divide both sides by 2
y= -1x/2+3
m= -1/2 but the slope of perpendicular lines is the negative reciprocal.
where in m=2
Second find b by substituting the 2 points given
x=8
y=3
3= 2(8)+b then solve
-16+3=b
b=-13
2nd equation: y=2x-13
Got it?
hope it helps :-)
12x + 4y = 16 4y = 16 - 12x y = -3x + 4 slope m1 = -3 (y = mx + c) 5y - 22 = -15x y = -3x + 22/5 slope m2 = -3 thus, both lines are parallel to each other since they have same slope