Question

Solve using the substitution method
x+3y=10
xy=7

Answer 1

What's the matter? You didn't like my method?

Answer 2

y = 1 and x = 7

Answer 3

Hmm that's weird lol. Yeah the two solutions that Juanita gave worked now I just have to go through it and make sure I understand it for the exam! Thanks for helping out guys I appreciate it!

Answer 4

Yeah, I made a calculation mistake. I hate Luis Rivera because he uses programs

Answer 5

Luis Rivera provided the two solutions, not Juanita by the way. Nevertheless, I found my calculation mistake and my method is still intact.

Answer 6

Yeah I just caught that lol. I need to prepare because I have to take up to calc 3 for my major and Im not very good at math ha. I just have to keep pushing I guess!

Answer 7

do you need me to show work

Answer 8

x + 3y = 10
x = 10 - 3y
x = 7/y

x = x
10 - 3y = 7/y

y(10-3y) = 7
10y - 3y^2 = 7

3y^2 - 10y + 7 = 0
3y^2-3y-7y+7 = 0
3y(y-1)-7(y-1)=0
(y-1)(3y-7)=0
y = 1
y = 3/7

x = 7
x = 3

Answer 9

There's my corrected solution

Answer 10

Juanita, there truly are two solutions

Answer 11

hero -- your 3rd line is incorrect - the solutions i gave are correct - you can not add 10-3y and get 7/7

Answer 12

juanita, do I need to put this in writing for you? nobody added 10-3y to get 7/7

Answer 13

You should plug the solutions back in and see what you get. For some reason, you're convinced your answer is correct when you have not even posted a solution

Answer 14

Hero

x + 3y = 10
x = 10 - 3y
x = 7/y

your 3rd line is incorrect - i meant to type 7/Y

Answer 15

how is that incorrect? Explain

Answer 16

Don't give me the bit about dividing by a variable because I multiply it back in

Answer 17

Which is totally valid

Answer 18

how can you combine 10-3y to get 7/y? that is not proper nor correct

Answer 19

You don't understand well enough, it is okay though.

Answer 20

It's called substitution by the way

Answer 21

Two expressions equal x:
x = 10 - 3y
x = 7/y

Now we set x = x meaning those two expressions are set equal:
x = x

10 - 3y = 7/y

If you don't understand that, I can't help you.

Answer 22

x+3y = 10
xy = 7

x = 10-3y
(10-3y)(y) = 7
10y -3y^2 = 7

using quadratic equation zeros are x = 7/3 and 1

subbing back in to xy = 7

y = 3/7 and 7

those are the actually correct answers.

Answer 23

sweetheart i was just telling you that your third line was incorrect. Have a great day

Answer 24

Actually, you didn't. Something is wrong with your answers.

Answer 25

The points are (7,1) and (3,3/7)

Answer 26

Your approach is incorrect. You either inputted it wrong or something.

Answer 27

Juanita, if you can find someone who agrees the my solution is not correct, I'll give you the respect you're looking for.

Answer 28

I see why you're confused now Juanita. I'll show you why my third line is correct:

\[xy = 7\]
\[\frac{xy}{y} = \frac{7}{y}\]
\[x = \frac{7}{y}\]

x = 7/y is my third line. These are the steps to get to the third line.