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Have I done this right? y = m x + b

b = 11 1/2 x = --6 and y = 5

to graph it, do it start at 11 1/2 on the x axis and then down 1 and over 2?
thanks

2007-11-29 16:56:02 · 3 answers · asked by Boo Radley 4 in Science & Mathematics Mathematics

3 answers

(- 6 , 5) and (- 2 , 3)
m = (3 - 5) / (- 2 + 6) = - 2 / 4 = - 1 / 2
y - 5 = (-1/2) (x + 6)
y = (-1/2) x - 3 + 5
y = (-1/2) x + 2

2007-11-29 21:41:29 · answer #1 · answered by Como 7 · 4 1

The line passes through (-6,5) and(-2,3)
To graph it, simply plot these 2 points, then draw your line through them. Extend the line in both directions a
bit, to indicate that it's not just a line segment you are
drawing.
A straight line only requires 2 points for it to be
graphed.

y=mx+b
The slope m= [y(2)-y(1)] / [x(2)-x(1)]
=5-3/ -6-(-2)
=2/-4, or -2/4, = -1/2
The required equation is y= -1/2(x)+b
Since the line passes through (-6,5) and (-2,3) either
point should satisfy the equation.
Using (-2,3), substitute the x and y values to find b
3= -1/2(-2)+b
3=1+b, and so b=2
The desired equation is y= -1/2 x +2

If you wanted to plot this line using this equation,
there are a couple of ways to do it.
Way#1:
The b term, 2, is the y-intercept. That's where the line cuts the y-axis. Mark a point on the y-axis 2 units
above the origin. ( Coordinates will be (0,2) ) That's
one point.
The slope is -1/2. The - sign tells me the line leans to
the left. Rise is -1, run is 2. Starting at the y-intercept
move UP 1 unit, then TO THE LEFT (the minus
direction) 2 units. Mark with a dot. Draw your line
through these 2 points.

Way#2
Set x=0, solve for y
Set y=0, solve for x
You can pick any number you want in fact, but the
choice of 0 makes calculations easy.
y= -1/2(x)+2
When x=0, y=2, Point is (0,2)
When y=0,x=, 0= -1/2(x)+2, -1/2(x)=-2, x=4 and the
Point is (4,0)
Plot these 2 points, draw line

2007-11-30 01:07:53 · answer #2 · answered by Grampedo 7 · 0 2

b is your y intercept.
because you have two points of a line you can find the slope.
(-6,5) (-2,3)
the slope formula: http://cs.selu.edu/~rbyrd/math/slope/
in order to fin the slope you would subtract the y values over the x.
(5-3)/(-6--3)=2/-3 which would be written: -2/3 b/c denominators, by rule are not supposed to have negative integers.
so your equation would then look like this:
y= -2/3x+ 11 1/2

2007-11-29 17:04:49 · answer #3 · answered by Draper 3 · 0 1

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