Math Question help needed
K so,
I've been asked to find the equation of the line which passes through the point with the given coordinates and has the given slope [i]m[/i]
The ordered pairs are (-2,-1) and the slope is 3/2.
This is from my sat math class which i've forgotten to do the homework from 2 weeks ago due to thanksgiving holiday lmfao; so i pretty much
forgot all the concepts taght
I googled some soltions, tried them ot (like b=y-mx) bt the answer key provided a diff answer
My answer was y=3/2x+(-4) which was wrong compared to 3x-2x=-4
October 16, 2010
7 Comments • Newest first
051035 has the correct solution.
Just show slope AB = slope BC
Slope AB = 17-12/3-2 = 5
Slope BC = 27-17/5-3 = 5
The alternative way is pretty silly IMO.
You can work out the equation of the line going through AB and sub in C.
If it agrees, C lies on the line.
I'll do it for the heck of it to show you.
Slope AB = 5
Point gradient form, using point A:
y - 12 = 5(x-2)
y - 12 = 5x - 10
5x - y + 2 = 0
Subbing in point C to check:
Left hand side:
= 5x - y + 2
= 5(5) -(27) + 2
= 0
= Right hand side
Therefore C lies on the line.
hmmmm.?K so last question:
I have 3 points : A(2,12) B(3,17) and c(5,27)
I already found out the equation of AB straight line
i need to show if the 3 points ABC lie on the same straight line
the equationsi 5x-7=-2
[quote=wuzzup]lol wdf did u do? o.o Looks so messed up.[/quote]
What's so messed up? It's just a point-gradient formula form lol.
@TS: go ahead and post your question
Okay thanks everyone, dr hye got me the correct solution
You know the slope, you know a point it passes through.
Point gradient form:
y - y1 = m(x-x1)
y - (-1) = (3/2)(x-(-2))
y + 1 = (3/2)(x+2)
Multiplying both sides by 2
2(y+1) = 3(x+2)
2y + 2 = 3x + 6
3x - 2y + 4 = 0
that looks a whole lots of number D: im only 12 </3 TT_TT
Well, the slope formula is y=mx+b, where m is the slope (which you know), and b is the y-intercept (which is where the line crosses the y-axis, when x=0).
Since you know the slope, and an ordered pair, you can solve for b by plugging the pair in.
y=mx+b
(-1)=(3/2)(-2)+b
(-1)=(-3)+b
2 = b
So now you have the y-intercept, so the equation is
y=(3/2)x + 2
I can't remember how to put it in that other form though...