Question

HELP ME WITH THIS PROBLEM PLEASE!

Solve with substitution method.
5x – y = –1
7x – 3y = 13

Answer 1

5x – y = –1
7x – 3y = 13

chose top or bottom equation in my case i chose top. SOlve for y or x i chose y since it looks simplest

5x-y=-1
-y=-1-5x subtract 5x from both sides.
y=1+5x multiply by -1 both sides to get rid of that negative.
WITH ME SO FAR?

now you substitude 1+5x into the y variable into either top or bottom equation. I chose top equation again

5x- (1+5x)=-1 Now solve for x
5x-1-5x=-1 distribute the -
-1=-1 from what i can see is that these 2 equations overlap. Meanin infinite many solutions. Or I did it wrong :P

Answer 2

I did it wrong somewhere let me check dbl check

Answer 3

Thank you so much<333

Answer 4

Oh okay

Answer 5

mathway says y=-9 and x=-2

Answer 6

I know :P

Answer 7

I think where i went wrong was that i chose to plug in (1+5x) into top equation. That is wrong. I think i should plug it into bottom equation lets try that
(1+5x)
7x – 3y = 13
7x – 3(1+5x) = 13 plugged in
7x-3-15x=13 distributed the -3
8x-3=13 added like term the 7x and - 15x = 8x
8x=16 add 3 to both sides
x=2 divide both sides by 8

YAY x=2 we more than half way done.

Answer 8

I thought x is -2?

Answer 9

(1+5x)
7x – 3y = 13
7x – 3(1+5x) = 13 plugged in
7x-3-15x=13 distributed the -3



-8x-3=13 added like term the 7x and - 15x = -8x HERE
^ ^
:( forgot the - sign

-8x=16 add 3 to both sides
x=-2 divide both sides by -8

YAY x=-2 we more than half way done.

Answer 10

Ok now for sure knowing x=-2 you plug it into bottom or top equation and solve for y

OR here is a neat trick you know from the first step how we figured out that

y=(1+5x)

when we solved for the top equation? Well use that

y=1+5(-2)
y=1-10 = -9

Answer 11

sorry i made so many little careless mistakes

Answer 12

It's okay, at least you helped and went back to fix them :)
Do you mind helping me with 2 more questions? :)))

Answer 13

Ask away brb in less than 10 minutes

Answer 14

Solve with elimination
2x + 9y = 4
3x + 7y = –7

I know that if I multiply the first eaution by -3 i'll get -6x for the fist term and if I multiply the second equation by 2 i'll get 6x for the first term. then I add them right? After that I'm lost lol

Answer 15

after adding them i got y=2. now what? lol

Answer 16

Well elimination means you wanna eliminate one of the xs or ys. ANd you do that by adding a multiple of top equation to bottom :) I'll explain more

Answer 17

2x + 9y = 4 eq 1
3x + 7y = –7 eq 2


We wanna eliminate the 3x in eq 2. By adding a multiple of eq 1 to it

3+2*X=0 solve for X notice it is capital X so dont confuse for x
2X=-3 subtract 3 from both sides
X=-3/2 divide by 2 both sides

so now you have that multiple that you should multiply by

So it should be
eq2+eq1*(-3/2)

eq1*-3/2 looks like this

(-3/2)* (2x + 9y = 4) =
-3x-(27/2)y=-6


now lets add. Imma do it by putting them on top of eachother
3x + 7y = –7 eq 2
-3x-(27/2)y=-6 eq1*(-1/3)
0 -(13/2)y=-13


as you can see we eliminated a x




-(13/2)y=-13

what you can do now is

y=-13/-(13/2) divide by -(13/2)
y=2

--- this is your original---
2x + 9y = 4
3x + 7y = –7


---after elimination----
2x + 9y = 4
-(13/2)y=-13


or

2x + 9y = 4
y=2


and you are done.

Unless they ask you to back substitude y=2 into top equation.

Answer 18

I dont need the value of x?

Answer 19

Wait I'm condused, Did I do mine wrong?

Answer 20

oh wait i think you do but all you have to do is back substitude :) since you know y=2 THen

2x+9y=4
2x+9*2=4 plugged in the 2 at y. Now just solve :)

Answer 21

Oh okay, Thank you :)

Answer 22

De nada

Answer 23

btw i dbld checkd and y is indeed 2 :D hope you can do the rest.

Answer 24

Okay, Last one I promise. lol

x – 2y < 18
4x + y > –5
Solve by graphing method

Answer 25

:) i'm sorry for being such a pain lol

Answer 26

do you know how to graph y=mx+b type of lines?

Answer 27

yeah, I think. I dont remember...

Answer 28

ookay wait. for the first equation i isolate y by subtracting x and divideing by -2? then i get -2/1 and -9?

Answer 29

Nevermind, I'm dumb. lol I dont know if I did it right.

Answer 30

x – 2y < 18
4x + y > –5

first we will convert both in terms of y

x – 2y < 18
-2y<18-x subtract x
y>-9+1/2x the sign flipped cuzz it is a rule of dividing or multiply by a - which we did cuzz we divided by -2
y>1/2x-9 rearange to y=mx+b mode but replace = with >
-----
4x + y > –5
y>-5-4x subtract 4x
y>-4x-5 rearrange.

so you have
y>1/2x-9
y>-4x-5

Answer 31

since

you have
y>...
y>... the > means shade above. Or that is how i interpret it. I am shading for the line that crosses the -5