SOLUTION: Write an equation of the line that passes through the given points. 1. (-1,3) , (1,-1) Also if you can explain how you can explain when you cross multiply. I don't get it a

Question 780271: Write an equation of the line that passes through the given points.
1. (-1,3) , (1,-1)
Also if you can explain how you can explain when you cross multiply. I don't get it at all if you can explain.
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Write an equation of the line that passes through the given points.
1. (-1,3) , (1,-1)
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slope = (-1-3)/(1--1) = -4/2 = -2
-------
Form: y = mx + b
Solve for "b":
-1 = -2*1 + b
b = 1
Equation:
y = -2x + 1
=======================
Also if you can explain when you cross multiply
----
If you have the form a/b = c/d
you can cross multiply to get ad = bc
-----
Example:::
If you have (x+3)/2 = (3x+1)/7 you can cross-multiply to get:
7(x+3) = 2(3x+1)
7x+21 = 6x+2
x = -19
=============
You can also cross-multiply if yo are adding or subtracting fractions::
Example:: (2/3) + (4/5)
= (5*2+3*4)/(3*5) = (10+12)/15 = 22/15
OR
(2/3)-(1/5) = (5*2-3*1)/15 = (10-3)/15 = 7/15
=========================
Cheers,
Stan H.
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