Question

x+y=42
80x+64y=2880
How do I graph this!?!?

Answer 1

Well we CAN put this in slope intercept form (but i advice just use a graphing calculator)

So we want to make both equations look like \(\large y = mx + b\)

The first is easy
\[\large x + y = 42\]

We can subtract 'x' from both sides of the equation to get

\[\large y = -x + 42\]

showing us that the slope would be -1 and the y-intercept would be 42

The second would be

\[\large 80x + 64y = 2880\]

Same thing...subtract 80x from both sides

\[\large 64y = -80x + 2880\]

And this time we need to divide everything by 64 because we want 'y' by itself so

\[\large y = -\frac{5}{4}x + 45\]

So now we have a slope of -5/4 with a y-intercept of 45

So it would look something like

Answer 2

where did you get the 42?

Answer 3

Well, the equations we came up with were

\[\large y = -x + 42\]
and
\[\large y = -\frac{5}{4}x + 45\]

The 42 in the first equation as well as the 45 in the second are the y-intercepts of those respective lines...meaning where they cross the 'y-axis' so I labeled them as such

Answer 4

yeah but when i put it on the graph they dont intersect