# MEI C3 question Methods of Proof

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i) Prove that if a and b are rational numbers, then a + b is a rational number.

ii) Give a counter-example to disprove the statement that if a + b is a rational number, then a + b are both rational numbers.

iii) Use the method of proof by contradiction to prove that if a is a rational number and b is an irrational number, then a + b is an irrational number.

OR maybe anyone here has access to the MEI maths website?

I desperately need answers to this question.

Question 2 from an additional exercise (Proof, section 1: methods of proof)

thank you!

ii) Give a counter-example to disprove the statement that if a + b is a rational number, then a + b are both rational numbers.

iii) Use the method of proof by contradiction to prove that if a is a rational number and b is an irrational number, then a + b is an irrational number.

OR maybe anyone here has access to the MEI maths website?

I desperately need answers to this question.

Question 2 from an additional exercise (Proof, section 1: methods of proof)

thank you!

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#2

(Original post by

i) Prove that if a and b are rational numbers, then a + b is a rational number.

ii) Give a counter-example to disprove the statement that if a + b is a rational number, then a + b are both rational numbers.

iii) Use the method of proof by contradiction to prove that if a is a rational number and b is an irrational number, then a + b is an irrational number.

OR maybe anyone here has access to the MEI maths website?

I desperately need answers to this question.

Question 2 from an additional exercise (Proof, section 1: methods of proof)

thank you!

**igor92**)i) Prove that if a and b are rational numbers, then a + b is a rational number.

ii) Give a counter-example to disprove the statement that if a + b is a rational number, then a + b are both rational numbers.

iii) Use the method of proof by contradiction to prove that if a is a rational number and b is an irrational number, then a + b is an irrational number.

OR maybe anyone here has access to the MEI maths website?

I desperately need answers to this question.

Question 2 from an additional exercise (Proof, section 1: methods of proof)

thank you!

Can't really give a hint; just think about it.

Assume a+b is rational (what does that mean) and then highlight the inconsistency in that rationality to safely assume a+b is irrational through contradiction.

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#5

(Original post by

Yes I know but I'm doing my induction. Lucky me

Thank you Small123

**igor92**)Yes I know but I'm doing my induction. Lucky me

Thank you Small123

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#6

(Original post by

Yes I know but I'm doing my induction. Lucky me

Thank you Small123

**igor92**)Yes I know but I'm doing my induction. Lucky me

Thank you Small123

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#10

That really looked like it was building up inside your head . A bit random however.

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#11

(Original post by

That really looked like it was building up inside your head . A bit random however.

**Farhan.Hanif93**)That really looked like it was building up inside your head . A bit random however.

edit - i know, let's not steal the thread, i'll stop lol.....

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#12

(Original post by

You ain't heard bro, July is the random month....random stuff happens, you should know that being a casanova.....random is up your alley jokes

**boromir9111**)You ain't heard bro, July is the random month....random stuff happens, you should know that being a casanova.....random is up your alley jokes

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#13

(Original post by

aha, Casanova.

**Farhan.Hanif93**)aha, Casanova.

**It may appear random but I know my stuff, trust me**
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#14

rational means 'can be written as a fraction' use that and work from there..

for example A + B

where A = m/n

and B = p/q

for example A + B

where A = m/n

and B = p/q

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#15

(Original post by

rational means 'can be written as a fraction' use that and work from there..

for example A + B

where A = m/n

and B = p/q

**Jonogodden**)rational means 'can be written as a fraction' use that and work from there..

for example A + B

where A = m/n

and B = p/q

edit - sorry, thought you was OP, didn't read his username lol, my bad....

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#16

(Original post by

thanks ur rlly unhelpful. can u just give some working pls instead of j saying i cant give a hint

**mariellas0005**)thanks ur rlly unhelpful. can u just give some working pls instead of j saying i cant give a hint

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#17

(Original post by

Did you mean to comment on a 9-year-old thread??

**davros**)Did you mean to comment on a 9-year-old thread??

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#18

(Original post by

um yes because i was doing the same question. why are u commenting then lol

**mariellas0005**)um yes because i was doing the same question. why are u commenting then lol

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#19

**mariellas0005**)

um yes because i was doing the same question. why are u commenting then lol

Tbh it's best to start a new thread of your own if there's a problem you're currently stuck on, rather than bumping a 9 year old thread

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#20

(Original post by

Seen as we aren't here to do the work for you, why would we offer more than hints? Seen as if you just copy what we tell you, you will learn nothing...

**zetamcfc**)Seen as we aren't here to do the work for you, why would we offer more than hints? Seen as if you just copy what we tell you, you will learn nothing...

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