How do I solve and graph this question --> x+3y=15

Question

I don't know how to get the graph... I get to y=-1/3x + 15 and get stuck.

Answer 1

Hi Nicole,

 

Given: x+3y=15

 

First things first is to get the given equation to be in slope intercept form in order to graph

 

slope intercept form --> y=mx+b

m= slope

b= y-intercept 

 

 

x+3y=15

 

Step 1: subtract x from both sides

 

3y=-x+15

 

Step 2: divide EVERYTHING by the coefficient of y, which is 3

 

y=-1/3x + 5

 

Now you have an equation of line. The next step would be to make a x-y plot so that you can graph. This means to pick random points for x, plug them into your new equation and find y. Typically you always want to pick numbers that are both positive and negative. So we'll make it easy and pick simple numbers since we're dealing with fractions and pick two negative numbers, and two positive numbers.

 

when x=-6, y=7

when x=-3, y=6

when x=0, y =5

when x=3, y=4

 

Now you have four ordered pairs {(-6, 7), (-3, 6), (0, 5), (3, 4)}

Graph the set above and you're done!!

 

 

Answer 2

Hello

 

Well

you are not getting the correct equation

 

x+3y=15

3y=-x+15

now divide 3 to both x and 15

y= -x/3 +15/3

 

so

y=-x/3+ 5

now pick points for x (i pick the easy one to solve for) and solve for y

 

x  | y

_____

-3 | 6

0  | 5

3  | 4

 

you can plot them on x-y coordinate plane and graph them.