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How do I write equations in slope-intercept form when I am given the slope(3) and a point(2,3)?

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2 Answers

Hi Edgar;
Slope-intercept form is...
y=mx+b
m is the slope.
b is the y-intercept, the value of y when x=0.
y=3x+b
We are given a point, (2, 3).  Let's plug it in...
3=3(2)+b
3=6+b
Let's subtract 6 from both sides...
-6+3=6+b-6
-3=b
The equation is...
y=3x-3
Well ... you're given that slope is 3 ... leads to KNOWING that the equation will be of the form y=3x+b (where b is the y-intercept).  So ... now plug in the given point, which lies on the line:  3 = 2*3 +b; 3 = 6 +b; subtract 6 from both sides, giving b = -3.
 
Now all is known:  the equation is y = 3x - 3 (or y = 3(x-1), if you'd like ... but, this is not in "pure" slope-intercept form).
 
 

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