Word problem solving

Question

What is the equation of the line that has a slope of -3 and passes through the point (-2,4)

A) y=-3x+4

B) y=-3x—4

c) y=-3x+2

d) y=-3x - 2

f) y=-3x

Answer 1

Start with point=slope form

(y - 4) = -3(x + 2)

Answer 2

There is a proper way to do this and also a quick way for exam.

Proper way:

Let's start with the slope- intercept form of a line: y=mx +b (We need to figure out m and b to know the equation of the line)

Since the slope of the line is -3, we know that m is equal -3. Hence, y=-3x+b

Now, because the line passes through the point (-2, 4), we can plug the x and y values in the above equation and find b: 4 = -3(-2) +b => 4= 6 + b => b=-2

Because m=-3, and b=-2, the equation of the line is d) y=-3x-2

Quick or sometimes easier way: Just plug the given x and y values in each of the choices to see it make sense (If you plug in the x and y values and see that the left and right sides of the equation are equal, then that is the correct answer).