Question

What is an equation of a line in point slope form that passes through the points (7,-8) and (-4,6)?

Answer 1

y=kx+b

for (7,-8): -8=7k+b. (function 1)

for (-4,6): 6=-4k+b (function 2)

Use function 2 - function 1

we get: 14=-11k

k=-14/11------>slope is -14/11

Now we know that first two options are wrong since they have the wrong slope for the function.

Plus -14/11 back to function 1/ or 2. Both are correct and can give you the answer. In this case I would plug it back to function 2.

6=14*4/11+b

b=66/11-56/11

b=10/11

We get y=-14/11x+10/11

subtract both side by 6.

y-6=-14/11x+10/11-66/11

y-6=-14/11x-56/11

y-6=-14/11(x+4)

So C is correct