Question

solve by graphing

20x+40y=240.00
10x+80y=300.00

Answer 1

@phi

Answer 2

this is from your previous problem?

Because the numbers are so big, I would simplify both equations first
(divide the first by 20 and the second by 10)

Answer 3

I got x+2y=12
x+8y=30

Answer 4

@phi

Answer 5

Are you supposed to graph these lines on paper, or with a computer ?

Answer 6

on paper

Answer 7

remember, you already know the answer (3 and 6 ? I forget which is x and which is y)
can you refresh my memory?

Answer 8

x is senior

Answer 9

x is 6

Answer 10

y is 3 @phi

Answer 11

that is where the lines will cross (this is cheating because we would not know that in advance).

x+2y=12

when x is 0, what is y ?

Answer 12

2

Answer 13

@phi

Answer 14

0 + 2y= 12

or
2y= 12
I would divide both sides by 2

Answer 15

i thought x would be 1

Answer 16

if you divide both sides by 2 it will be 6

Answer 17

yes. The idea is
x+2y=12

is a line and that means for each x value, there is a y value i..e you get an (x,y) point
for example when you make x=0
you get
0+2y =12
2y= 12
y= 6 (after dividing both sides by 2)

so (0,6) is on the line

can you plot that point ?

Answer 18

yes

Answer 19

if you choose x=1 we get
1+2y= 12
2y = 11 (after add -1 to both sides)
y= 11/2
that is a pain to plot.

Try x= 2

2+2y= 12
can you find y ?

Answer 20

5

Answer 21

so (2,5) is another point

plot that point.

then draw a line through the two points
and as a check , remember this line should also go through (6,3)

Answer 22

why would 2,5 be another point

Answer 23

why are we using 2,5 i thought we had to solve x+8y=30

Answer 24

can i also help

Answer 25

sure

Answer 26

we are still doing the first line.
to plot a line, you need two points
we found two points on the first line.

Answer 27

when i do it it ends up as a slope intercept dont know if its right

Answer 28

ooo ok @phi

Answer 29

once you plotted the two points, draw a line through them

(and be sure the line goes thought (6,3)

Answer 30

brb

Answer 31

okay it does

Answer 32

now we do the 2nd line

Answer 33

x+8y=30

Answer 34

80y=300.00

Answer 35

(0,3.75)

Answer 36

yes, but it's hard to plot fractions
also, it's easier to use the equation after we simplified it
(notice if we use
x+8y=30
with x=0 we get
8y= 30
y= 30/8 = 3.75

Answer 37

x+8y=30

if we make y=0 we get x=30 so (30,0) is on the line
but that point is a bit far away ... it depends how big your graph paper is

but if we let y= 2, we get x+8*2= 30
and x+16=30
x= 14
so (14,2) is a good point

try y = 4 in x+8y= 30

Answer 38

x+32=30

Answer 39

ok , now add -32 to both sides

Answer 40

2

Answer 41

-2

Answer 42

yes, x=-2
so (-2,4) is a point.

can you plot
(-2,4) and (14,2)
and draw a line through the points ?
(and be sure it goes through (6,3)

Answer 43

The final result should look like this

Answer 44

thank you @phi