MYTUTOR SUBJECT ANSWERS

353 views

How can I find x and y?

Many students ask how they can they find 2 unknowns,given 2 simple equations. I'll try to focus in this answer on giving students a tool which they can use to solve ANY 2 simple equations with one solution.Let's take an example:

5*x+y=22 and 3*x+4*y=20

In short,the plan is to:

1.) Write y in terms of x from the first equation

2.) Substitute it in the second one, so that we will get only an equation in function of x

3.)Then, find x from it.

4.)Now, we can substitute x's value in the first equation and find y.

Concrete:

1.) Write y in terms of x from the first equation

From 5*x+y=22 we get that y=22-5*x.

2.) Substitute it in the second one, so that we will get only an equation in function of x

Substituing y in the second equation gives :

3*x+4*(22-5*x)=20.

3.)Then, find x from it. 

We now rearrange it ,so:

3*x+88-20*x=20(we opened the parenthesis)

Therefore:

88-17*x=20(we gave x as common factor and had x*(3-20) which is -17*x)

Therefore by adding 17*x and subtracting 20 we get :

68=17*x.

By dividing the equation with 17 we have x=4.

4.)Now, we can substitute x's value in the first equation and find y. 

So we substitute it in the first equation,so 5*x+y=22 gives 5*4+y=22,so y=2. 

The beauty of this method stays in the fact that it can be used to solve any problem like that.

Now,with some practice,you should be able to find the solution of a similar problem. Here are some exercises which you could use to practice some more :

1.)  3*x+7*y=10 and x+5*y=6

2.)  x+y=9 and 3*x+4*x=32

3.)  x+y=6 and x+5*y= 26

4.) 4*y=28 and 2*x+y=9

5.) 6*x-2*y=72 and x+2*y=12

I would finally recommend not to memorise the steps of this method,but to understand them. Good luck !

Solutions:

1.) x=1 and y=1

2.) x=4 and y=5

3.) x=1 and y=5

4.) x=1 and y=7

5.) x=12 and y=0

Marco-Iulian G. GCSE Maths tutor, Uni Admissions Test .MAT. tutor, A ...

12 months ago

Answered by Marco-Iulian, a GCSE Maths tutor with MyTutor

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

335 SUBJECT SPECIALISTS

£18 /hr

Grace J.

Degree: Biological Sciences (Bachelors) - Exeter University

Subjects offered: Maths, Extended Project Qualification+ 2 more

Maths
Extended Project Qualification
Chemistry
Biology

“I'm a Biological Sciences student in my 3rd and final year at the University of Exeter. I have a passion and enthusaism for all things science and computer based and hope to encourage this love through my tutorials.  I am a very patie...”

£20 /hr

Amruni C.

Degree: Medicine (Bachelors) - Imperial College London University

Subjects offered: Maths, Science+ 1 more

Maths
Science
-Medical School Preparation-

“Hi, I’m Amruni and I’m a medical student at Imperial College London. For the past 2 years I have been tutoring Maths and Science to students from 11+ to GCSE and have absolutely loved being able to share my passion for science and mat...”

£22 /hr

James B.

Degree: History (Research) - Bristol University

Subjects offered: Maths, History+ 3 more

Maths
History
Chemistry
Biology
-Personal Statements-

“About Me:This year (2015) I am undertaking a research degree (MPhil) in History at the University of Bristol. Last year I graduated with a Bachelor's degree with honours also in history at the Uinversity of Bristol. I am going to sta...”

About the author

£18 /hr

Marco-Iulian G.

Degree: Mathematics&Computer Science (Masters) - Bristol University

Subjects offered: Maths, Further Mathematics + 2 more

Maths
Further Mathematics
.STEP.
.MAT.

“I'm in my first year at University of Bristol, studying Mathematics and Computer Science MEng. From an early age I started to participate in lots of contests and maths olympiads, and the experience I achieved along the way enriched bo...”

You may also like...

Posts by Marco-Iulian

How can I find x and y?

How do I make calculations with percentages?

How do I solve a quadratic equation?

How do you solve this problem?

Other GCSE Maths questions

How do i solve the quadratic x^2 + 5x + 6 = 0 ?

How do I calculate the gradient of a linear (straight) graph?

The first three terms of a sequence are a, b, c. The term-to-term rule of the sequence is 'Multiply by 2 and subtract 4'. Show that c = 4(a – 3).

How do you factorise a quadratic equation?

View GCSE Maths tutors

Cookies:

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

mtw:mercury1:status:ok