Question 239583
The Point-Slope Form formula is: {{{y-y1=m(x-x1)}}}
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All you need to do here is substitute the values and solve for missing value.
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m=-1  (m=slope)
y=-2
y1=7
x=k
x1=-1  (the missing value)
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{{{y-y1=m(x-x1)}}}
{{{-2-7=-1(k-(-1))}}}
{{{-9=-1(k+1)}}}
{{{-9=-k-1}}}
{{{-8=-k}}}
Now divide by -1 on both sides to determine the value of k.
{{{8=k}}}
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Done!