What is the equation of a line that goes through #(7, -7)# and has a slope of #-3#?

1 Answer
Tony B
Nov 19, 2015

You use standard form of #y=mx+c# and substitute in the given values to find the value of c

#y =(-3)x+14#

Explanation:

Using #y=mx+c# and universal notation of #(x,y)#

Let #y= -7#
Let #x=7#
Let #m=-3color(white)(xxx)# (this is fixed. It does not change!)

Giving:

#-7=(-3)(7) +c#

#-7 = -21+c#

Add +21 to both sides:

#-7 +21 = -21+21+c#

#14=0+c#

#c=14#

So the full equation of the line is:

#y =(-3)x+14#

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