MYTUTOR SUBJECT ANSWERS

4096 views

How do you solve the simultaneous equations 3x + 4y = 5 and 2x – 3y = 9

We label each equation

3x + 4y = 5 (1)

2x – 3y = 9 (2)

We now want to get rid of one of the variables (x or y). Lets get rid of x:

We need (1) and (2) to have the same number of x's so we multiple (1) by 2 and (2) by 3 so they both have 6 x's

6x + 8y = 10 (1)*2

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

Now to get rid of the x's we take one of the equations from the other. It is easier to do (2)*3 -(1)*2

  6x - 9y = 27 (2)*3

- 6x + 8y = 10 (1)*2

                                   

     -17y = 17 

If we devide this equation by -17 we get

y = -1

We can plug this value of y into (1) to get

3x -4 = 5

add 4 to both sides of the equation

3x = 9

Divide by 3

x = 3

Now to check put x and y into (2)

6 - (-3) = 9 

As this is true, we have the solution

x = 3, y = -1

Sahiti S. GCSE Maths tutor, A Level Economics tutor, A Level Maths tutor

2 years ago

Answered by Sahiti, a GCSE Maths tutor with MyTutor


Still stuck? Get one-to-one help from a personally interviewed subject specialist

466 SUBJECT SPECIALISTS

£20 /hr

Shreya G.

Degree: Biochemistry with molecular medicine (Bachelors) - Nottingham University

Subjects offered:Maths, Biology+ 1 more

Maths
Biology
-Personal Statements-

“I am a first year undergraduate student at The University Of Nottingham, currently studying Biochemistry with molecular medicine. ”

£18 /hr

Liam R.

Degree: Economics (Bachelors) - Durham University

Subjects offered:Maths

Maths

“I study Economics at Durham. I have a passion for maths and hope to share this with you! To find out more, click on my profile & book a free 15-minute meeting!”

£22 /hr

Runzhi C.

Degree: Medicine (Bachelors) - Imperial College London University

Subjects offered:Maths, Chemistry+ 3 more

Maths
Chemistry
Biology
-Personal Statements-
-Medical School Preparation-

“Hi there, I am a first year medical student at Imperial College London and I have lived in the UK all my life. I enjoy studying medicine because it encompasses both scientific knowledge and social aspects. I am relatively new to tutor...”

About the author

Sahiti S. GCSE Maths tutor, A Level Economics tutor, A Level Maths tutor

Sahiti S.

Currently unavailable: for new students

Degree: Natural Sciences (Bachelors) - Durham University

Subjects offered:Maths, Economics

Maths
Economics

“Hi, my name is Sahiti and I am a second year natural sciences student (studying maths, economics and computer science).  Why me? I am passionate about both maths and economics, which both make up a major part of my degree. I l love t...”

You may also like...

Posts by Sahiti

How do you solve the simultaneous equations 3x + 4y = 5 and 2x – 3y = 9

If x = cot(y) what is dy/dx?

What is the Current Account

Other GCSE Maths questions

Solve 4x + 6 = 3

Find the highest common factor (HCF) of 12 and 18.

Find the equation of the line passing through the point ( 2, −3) which is parallel to the line with equation y + 4x = 7

Solve the simultaneous equations 4x + 7y = 1 and 3x +10y = 15.

View GCSE Maths tutors

We use cookies to improve your site experience. By continuing to use this website, we'll assume that you're OK with this. Dismiss

mtw:mercury1:status:ok