Question

I dont get this, please help.

Answer 1

Q1. P2
http://www.xtremepapers.com/CIE/International%20A%20And%20AS%20Level/9709%20-%20Mathematics/9709_s07_qp_1.pdf

Answer 2

can't find it ..

Answer 3

If you want to see the solution,
check this out,
http://www.xtremepapers.com/CIE/International%20A%20And%20AS%20Level/9709%20-%20Mathematics/9709_s07_ms_1.pdf

Answer 4

so many questions ... i can't find which question is Q1 P2

Answer 5

Question 1 on page 2.
http://www.xtremepapers.com/CIE/International%20A%20And%20AS%20Level/9709%20-%20Mathematics/9709_s07_qp_1.pdf

Answer 6

@experimentX : the first question on da second page

Answer 7

I didnt get it either... .

Answer 8

Find the value of the constant c for which the line y = 2x + c is a tangent to the curve y2 = 4x.

Answer 9

Yes

Answer 10

good Question. :)

Answer 11

let's try it ...
using implicit differentiation we get, 2y dy/dx = 4

Answer 12

Did you just try to give me a virus?

Answer 13

lol it was challenging but i think i might have the answer...

Answer 14

That pdf file you posted isn't working for me.

Answer 15

Nevermind.... I screwed up

Answer 16

@Hero it's working for all others.

Answer 17

Lol @ewokkman1

@experimentX , it's not in the marking scheme. :l

Answer 18

lol,saifoo,u made me rofled

Answer 19

I'm sure it would work for me, but malwarebytes says that the website is potentially malicious.

Answer 20

or, dy/dx = 2/y

now slope = 2/y = from line 2 => y=1
form eqn of parabola, x = 1/4

putting those values on line we get, 1 = 1/4*2+c
c = 1/2

????

Answer 21

@experimentX , Perfect. answer's correct. but please look at the marking scheme the method is different.
i will only get marks for C = 1/2.

http://www.xtremepapers.com/CIE/International%20A%20And%20AS%20Level/9709%20-%20Mathematics/9709_s07_ms_1.pdf
Page 4.

Answer 22

@Ultra_mysterious . lol, how?

@Hero , no idea.

Answer 23

ahh .. quite sweet method, without using calculus

Answer 24

How they did it? any ideas?

Answer 25

yeah ...

Answer 26

i personally like your method though.

Answer 27

they solved a parabola with a line, it should give you a solution, that is a point

Answer 28

y2 = 4x is a parabola, and y = 2x+c is a line

now if I replace y2 from line, when it will give me a quadratic equation on x

Answer 29

But wait. let's stick to your method.

how you got 2/y ?

Answer 30

the values of x will be those points where parabola intersects with the line.

Answer 31

x = 1/4 y2

Answer 32

ah .. my method, i used implicit differentiation to calculate slope.

Answer 33

and i compared slopes.

Answer 34

i like that one. please elaborate. :D

Answer 35

just switch x and y and you get the same much easyer

Answer 36

we have equation y2 = 4x

differentiate on both sides => 2y dy/dx = 4
or dy/dx = 2/y and we know dy/dx gives slope of tangent.

Answer 37

and we have tangent, y = 2x+c just compare the slopes, that will give the solution for y, then everything will unravel easily.

Answer 38

Why you took derivative of both sides?
why not
\[y = \sqrt{4x}\]?And now take the derivative?

Answer 39

it would do, but i prefer implicit differentiation.
yeah => dy/dx will give the slope of the tangent

Answer 40

Alright, after slope what you did?

Answer 41

you know the slope of tangent from line.

Answer 42

what's this?

form eqn of parabola, x = 1/4

Answer 43

no .. from the equation of line. since the line is the tangent/