Question 950813
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Find an equation of the line containing the given pair of points? (-7,-2)and(-5,-9)
Find the slope: m = {{{((y2-y1))/((x2-x1))}}}
Assign the given pairs as follows
x1=-7; y1=-2
x2=-5; y2=-9
Find the slope
m = {{{((-9-(-2)))/((-5-(-7)))}}}
minus a minus is a plus
m = {{{((-9+2))/((-5+7))}}} = {{{(-7)/2}}} 
Use the form y = mx + b, where y=-2 and x=-7 and m = {{{-7/2}}}
-2 = {{{-7/2}}}(-7) + b
-2 = {{{49/2}}} + b
lets us the decimal here
-2 = 24.5 + b
-2 - 24.5 = b
-26.5 - = b
b = -26.5
the equation then
y = {{{-7/2}}}x - 26.5
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Confirm this for yourself. 
substitute the given x's and ensure they equal the given y's