Question

Use the form y = mx + b for linear equation.

{(x,y): (1,2), (2,5), (3,8),...}

The answer is y = 3x - 1
I know how to get 3x it's by

(5-2)/(2-1)= 3÷1=3
(8-5)/(3-2)= 3÷1=3
(8-2)/(3-1)= 6÷2=3

What I don't understand is how to get the -1

Answer 1

so you have y=3x+b
to find b you need to take a point on y=mx+b
say (1,2)
y=3x+b
replace x with 1 and replace y with 2
2=3(1)+b <--solve for b

Answer 2

So then it would be 2 = 3(1) + b

3(1) = 3 so I'd have to carry 3 to the other side so its, -3 + 2 = b and I'd get -1

That solves b so you then write y = 3x -1? or did I do that wrong...

Answer 3

that's right
and (2,5) should work too
y=3x+b
5=3(2)+b
5-6=b
-1=b

Answer 4

you see see for any point in that set you will get the b value to be -1

Answer 5

Thank you! I actually understand it, not even that hard.