Complicated GCSE Maths Questions - Official Help Thread (All exam boards)

Post difficult A/A* questions and we will all help each other get our heads around them.

Two Questions for AQA (Specification 4360) - 19th June 2012, Unit 2
Question 17

Question 18
Here is an identity (3x + c)(x + c) ≡ 3x² – dx + 16
c and d are integers. Work out all possible pairs of values of c and d.

(edited 7 years ago)

Reply 1

chrisandmaddy

1

Question 18

expand out brackets as normal....you will get 3x^2+3xc+cx+c^2=3x^2-dx+16

x^2 terms of left hand side have to equal x^2 terms on right hand side....
x terms on left hand side have to equal x terms on right hand side...
number term(constant) on left hand side have to equal number terms on right hand side...

3x^2=3x^2....x=3

c^2=16......c=4 (squareroot)

3c+c= -d.....sub in c to get........3(4)+4=-d..........12+4= -d......d=16

(edited 7 years ago)

Reply 2

k2sigma

10

Hi guys,
created these questions myself and are very challenging. These types of questions are usually found at the end of the paper and require logical thinking and problem solving skills. The document i've attached contains 3 questions, ordered from easiest to hardest. Give them ago and tell me how you found those questions. If you become stuck simply ask, and i can help you out.

PS - the document is just named predicted questions because i was going to make predicted questions but then thought, leave it. So i just made random ones.

THE SOLUTIONS WILL BE ADDED BY TOMORROW AS I AM CURRENTLY REVISING ADD MATHS.

(edited 7 years ago)

Predicted Questions for Edexcel Paper 2.docx43.0KB

Reply 3

Oblivion99

11

Original post by chrisandmaddy

expand out brackets as normal....you will get 3x^2+3xc+cx+c^2=3x^2-dx+16

x^2 terms of left hand side have to equal x^2 terms on right hand side....
x terms on left hand side have to equal x terms on right hand side...
number term(constant) on left hand side have to equal number terms on right hand side...

3x^2=3x^2....x=3

c^2=16......c=4 (squareroot)

3c+c= -d.....sub in c to get........3(4)+4=-d..........12+4= -d......d=16

LOOOL. He asked for possible answers, not the actual thing. P.S I think your wrong.

Reply 4

Oblivion99

11

Original post by gurpartapl

Hi guys,
created these questions myself and are very challenging. These types of questions are usually found at the end of the paper and require logical thinking and problem solving skills. The document i've attached contains 3 questions, ordered from easiest to hardest. Give them ago and tell me how you found those questions. If you become stuck simply ask, and i can help you out.

PS - the document is just named predicted questions because i was going to make predicted questions but then thought, leave it. So i just made random ones.

THE SOLUTIONS WILL BE ADDED BY TOMORROW AS I AM CURRENTLY REVISING ADD MATHS.

Just I need the answer to the first one.

Reply 5

chrisandmaddy

1

oops sorry if got wrong end of stick! :smile:

ps....im right!!! :smile:

its called comparing coefficients!

(edited 7 years ago)

Reply 6

OscarTG

1

Question 17:
Line ABC is 2x + y = 6
Hence y = -2x + 6
y = mx+c, where c is y-intercept, hence y-intercept = 6. Therefore POINT B = (0,6)

POINT A crosses the x-axis, hence its y value = 0
Hence y = mx + c ----> 0 = -2x + 6 --> 2x = 6 ---.> x=3
Hence POINT A = (3,0)

A=(3,0), B=(0,6)=(3-3, 0+6)
B is midpoint, so POINT C is (0-3, 6+6) = (-3, 6)

POINT D is on the x-axis, so its y value = 0, therefore POINT D = (-7, 0) [and].
gradient = change in y/change in x = (yc - yd)/(xc - xd)
m = (6-0)/(-3--7) = 6/4 = 3/2 or 1.5
y = mx +c ----> y = 1.5x + c

Then use: y-yd = m(x-xd) to find equation of line (where m=1.5, as previously established):
y - 0 = 1.5x - 1.5*-7 = 1.5x + 10.5

Hence y = 1.5x + 10.5
or: 2y = 3x + 21

(edited 7 years ago)

Complicated GCSE Maths Questions - Official Help Thread (All exam boards)

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