Why is 3 negative?

Question

My teacher showed us the answer key to the study guide for finals, and the fraction to graph was 3x+5y=-20. I changed it to slope intercept form and got y=3/5x-4. But the answer key showed that it's y=-3/5x-4. Why is the 3 negative?

Answer 1

Just perform the algebraic steps to get an equation in the form y = mx + b.  Start with

 

3x + 5y = -20

 

Subtract 3x from both sides:

 

5y = -3x - 20

 

Divide both sides by 5:

 

y = (-3/5)x - 4

Answer 2

Yes, that answer,  y=-3/5x-4 is correct

 

If you have 3x+5y=-20 then you have to express y in term of x, so what you do is

 

5y=-20-3x and then you divide both sides by 5, So the slope is with minus sign =-3/5. Answer sheet didn't lie.