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how to find this equation in intercept form (-2,4)and(3,-1)

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3 Answers

Line equation in intercept form: x/a + y/b = 1, where a is the x-intercept, and b is the y-intercept of the line.
slope m = (4+1)/(-2-3) = -1 = -b/a
So, x+y = constant
Plug in (-2, 4),
x+y = -2+4 = 2
 
Answer: x/2 + y/2 = 1
Hi Jala;
(-2,4) and (3,-1)
Let's establish slope.
m=(y-y1)/(x-x1)
m=(4--1)/(-2-3)
Subtracting a negative number is the same as adding a positive number...
m=(4+1)/(-2-3)
m=5/-5=-1
y=-1x+b
y=-x+b
y=mx+b is the slope-intercept formula.  Slope is represented by m, and the y-intercept, the value of y when x=0, is represented by b.
y=-x+b
Let's plug in one set of coordinates..
4=-(-2)+b
4=2+b
Let's subtract 2 from both sides...
4-2=2+b-2
2=b
y=-x+2
 
Let's check our work using the other set of coordinates...
-1=-(3)+2
-1=-3+2
-1=-1
Once you found the value of the slope, it's better to use point-slope form of linear equation for this kind of problems.

(y - y1) = m(x - x1)

y - 4 = -1[x - (-2)]  

y = -1(x + 2) + 4

y = - x - 2 + 4

y = - x + 2

Comments

Hi Nataliya;
I understand what you are saying.  However, after establishing slope, I prefer to use the slope-intercept formula with one set of coordinates, and then checking my answer with the other set of coordinates.  Going from establishing slope into point-slope formula, does not allow an alternate to check my work.