I'm really stuck on this simultaneous equation

Watch
Rockyboy
Badges: 11
Rep:
?
#1
Report Thread starter 6 years ago
#1
The question is
Solve the simultaneous equations
y = 3x – 1
x² + y² = 5

My teacher gave us the answer but i'm not sure how she got the answer please help.
0
reply
CH :)
Badges: 2
Rep:
?
#2
Report 6 years ago
#2
You need to substitute the first equation into the second so you'd get x2 +(3x-1)2 =5
0
reply
Rockyboy
Badges: 11
Rep:
?
#3
Report Thread starter 6 years ago
#3
(Original post by CH :))
You need to substitute the first equation into the second so you'd get x2 +(3x-1)2 =5
so where does the y go?
0
reply
Zen-Ali
Badges: 8
Rep:
?
#4
Report 6 years ago
#4
(Original post by Rockyboy)
...
I'm presuming that's supposed to be:

y = 3x - 1 \ (1)

x^2 + y^2 = 5 \ (2)

If so, looking at the first equation, you have y in terms of x. Therefore, how can you change equation 2 to get an equation just in x?

Hint
Try substituting equation 1 into the y^2 of equation two.


If it helps, visualise equation one as 3x - 1. Because that is equal to y, you're effectively saying that y^2 = ... \ ?. I hope that is of help.
0
reply
Macleod11
Badges: 2
Rep:
?
#5
Report 6 years ago
#5
Y = 3x-1. That's what y is. So the y just goes because it IS 3x-1.


Posted from TSR Mobile
0
reply
CH :)
Badges: 2
Rep:
?
#6
Report 6 years ago
#6
You substitute the y into the second to find out your x values, then you use your x values and the first equation to work out y after
0
reply
Rockyboy
Badges: 11
Rep:
?
#7
Report Thread starter 6 years ago
#7
(Original post by CH :))
You substitute the y into the second to find out your x values, then you use your x values and the first equation to work out y after
so the equation will be x² + (3x-1)² =5 when you substitute y into equation 2 ?
1
reply
CH :)
Badges: 2
Rep:
?
#8
Report 6 years ago
#8
Yep
0
reply
CH :)
Badges: 2
Rep:
?
#9
Report 6 years ago
#9
So expand, simplify and you should have a quadratic that can be factorised
0
reply
Rockyboy
Badges: 11
Rep:
?
#10
Report Thread starter 6 years ago
#10
This makes it much more easier. Thanks to all those who helped me
0
reply
CH :)
Badges: 2
Rep:
?
#11
Report 6 years ago
#11
No problem
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Current uni students - are you thinking of dropping out of university?

Yes, I'm seriously considering dropping out (137)
14.41%
I'm not sure (42)
4.42%
No, I'm going to stick it out for now (286)
30.07%
I have already dropped out (24)
2.52%
I'm not a current university student (462)
48.58%

Watched Threads

View All
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise