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Help with A level maths?

Minnie16

For 83 I keep getting a repeated root where X=-2 but the answer should be C not A. Please explain ...

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Reply 1

RDKGames

Study Forum Helper

Original post by Jas1947

For 83 I keep getting a repeated root where X=-2 but the answer should be C not A. Please explain ...

Well firstly; x=-2 is not a root. Secondly, in the case where you WOULD get a repeated root, that would account for 2 answers unless the question specifies "how many distinct real roots are there?" in which case the repeated root would account for 1, I believe.

Reply 2

B_9710

Original post by Jas1947

For 83 I keep getting a repeated root where X=-2 but the answer should be C not A. Please explain ...

There is no repeated root.

Reply 3

alhrona

x= 0 is a solution aswell

Reply 4

NeverLucky

That's the question from the Cambridge specimens pre-interview paper isn't it? I wasn't sure if there's a better method but I differentiated and found the values that correspond to turning points. Found the co-ordinates of the turning points and just considered how the graph would look like. You'll find it'll cross the x-axis twice.

Reply 5

B_9710

Original post by alhrona

x= 0 is a solution aswell

No it isn't.

Reply 6

NeverLucky

Original post by alhrona

x= 0 is a solution aswell

Um...no. If

x=0

then

-10 = 0

which doesn't make sense.

Reply 7

alhrona

Original post by B_9710

No it isn't.

if you factorise it you get 2 solutions of x=0 from a xsquared

Reply 8

alhrona

Original post by NeverLucky

Um...no. If

x=0

then

-10 = 0

which doesn't make sense.

oh yeah , excuse me , it's been over a month since the exams so i have forgotten everything

Reply 9

RDKGames

Study Forum Helper

Original post by alhrona

if you factorise it you get 2 solutions of x=0 from a xsquared

wot????

Reply 10

B_9710

Original post by alhrona

if you factorise it you get 2 solutions of x=0 from a xsquared

There's a stationary point at x=0, not a root.

Reply 11

Zacken

Original post by alhrona

if you factorise it you get 2 solutions of x=0 from a xsquared

You might want to read the "don't answer if you don't know what you're talking about at all" bit of the posting guide stickied at the top of the forum.

Reply 12

EnglishMuon

Alevel maths threads get me like

Reply 13

Uni12345678

I have no idea if this is correct or not, but...

EDIT : sorry just realised the last part is a little wrong , b squared - 4ac = -2 squared - 4(1)(-root10) so should be 4 + 4root10 so still 2 real roots but not 16 + 4root10

(edited 7 years ago)

Reply 14

Bath~Student

Original post by Zacken

You might want to read the "don't answer if you don't know what you're talking about at all" bit of the posting guide stickied at the top of the forum.

Well, it's fabulous to see that Zacken's attitude is just as bad - if not worse - as when I used to pester him months ago.

The Cambridge snobbery is really coming on well, I see.

Reply 15

Bath~Student

Original post by Uni12345678

I have no idea if this is correct or not, but...

Lovely - all correct.

Reply 16

Student403

Original post by Bath~Student

Well, it's fabulous to see that Zacken's attitude is just as bad - if not worse - as when I used to pester him months ago.

The Cambridge snobbery is really coming on well, I see.