Question

(-2,-21)(3,4)(-7,-46), they satisfy a linear relationship, what is the value of x when y= 14?

Answer 1

I got an answer earlier, but I didn't understand how you got from a to b :O

Answer 2

Pick any two of these points. They must be located on some line, which can be described using an equation of form:

y = ax + b

Using x and y values from the points you selected and a system of 2 equations like the one above, find a and b that satisfy it.

Then solve using y = 14.

Answer 3

I'm still a little lost. I understand that you do that, however when you get:

-21=-2a+b and 4=3a+b how do you then get

-25= -5+b?

Answer 4

A small mistake there: -21 = -2a + b

Answer 5

Oh yes. Can you explain how you get there? Am I supposed to automatically assume that you subtract in this eqution?

Answer 6

Sure. Let's start with the points you picked. We get:

-21 = -2a + b
4 = 3a + b

Let's calculate 'b' using the first equation:

b = -21 + 2a

Now we put it in the 2nd one:

4 = 3a + (-21 + 2a)

Simplification gives us:

4 = 3a - 21 + 2a
5a = 25
a = 5

Now we use the calculated value of 'a' in the first equation:

b = -21 + 2a
b = -21 + 2 * 5
b = - 21 + 10
b = -10

So the line you're looking for is given by the equation:

y = 5x - 10

Answer 7

So you're subsituting in the equations to find the ultimate answer?

Answer 8

I used the substitution method, yes.

Answer 9

Thank you :D

Answer 10

Welcome!