Every nonvertical line in the coordinate plane can be described by an equation of the form $\,y = mx + b\,$, where:
The equation $\,y = mx + b\,$ is called the slopeintercept form of the line.
Two different points uniquely determine a line.
One point and a slope also uniquely determine a line.
This web exercise gives you practice writing the equation of the line in these two situations.
$y = mx + b$  (A line with slope $\,3\,$ isn't vertical, so it can be described by an equation of this form.) 
$y = 3x + b$  (Substitute the known slope, $\,3\,$, in for $\,m\,$. Next, we must find $\,b\,$.) 
$5 = 3(1) + b$  (Since $\,(1,5)\,$ lies on the line, substitution of $\,1\,$ for $\,x\,$ and $\,5\,$ for $\,y\,$ makes the equation true.) 
$5 = 3 + b$  (simplify) 
$\,b = 8\,$  (add $\,3\,$ to both sides; write in the conventional way) 
$y = 3x + 8$  (substitute the nowknown value of $\,b\,$ into the equation) 
$y = mx + b$  (start with slopeintercept form) 
$y = 3x + b$  (substitute the nowknown slope, $\,3\,$, in for $\,m\,$) 
$4 = 3(1) + b$ 
(Which point should you use?
It doesn't matter! In general, try to choose the simplest numbers to work with.) 
$4 = 3 + b$  (simplify) 
$\,b = 1\,$  (subtract $\,3\,$ from both sides; write in the conventional way) 
$y = 3x + 1$  (substitute the nowknown value of $\,b\,$ into the equation) 
CONCEPT QUESTIONS EXERCISE:
On this exercise, you will not key in your answer.However, you can check to see if your answer is correct. 
PROBLEM TYPES:
