All igcse questions

**darkpinkish** · March 12th 2010, 11:41 AM

hey everybody

i couldnt figure out this question from a past paper about quadratic formula
it was pretty straight foward-
the total area of rectangle R and Q is 64cm^2
calculate the value of x correct to one decimal place
5x^2+30x+24
i got 0.95 (for subtraction) and 5.05

i am jus confused on what i am suppose to choose so that the answer is 64
plus forgot what it meant by correct to one decimal place...was it rounding up?

...n also 3 significant figures....actually i m mixed up in both of them -.-

thanks

**e^(i*pi)** · March 12th 2010, 11:45 AM

Originally Posted by darkpinkish

hey everybody

i couldnt figure out this question from a past paper about quadratic formula
it was pretty straight foward-
the total area of rectangle R and Q is 64cm^2
calculate the value of x correct to one decimal place
5x^2+30x+24
i got 0.95 (for subtraction) and 5.05

i am jus confused on what i am suppose to choose so that the answer is 64
plus forgot what it meant by correct to one decimal place...was it rounding up?

...n also 3 significant figures....actually i m mixed up in both of them -.-

thanks

From what I can gather 64 is what the quadratic function is equal to.

$5x^2-30x+24=64$ which is equal to $(x-2)(x-4)=0$

I have no idea how you got the quadratic

**darkpinkish** · March 12th 2010, 11:54 AM

same here...but the asnwer is 1.1,
from the first part of the question i've arrived to 5x^2+30x+24
and the second part said find x correct 1 decimal place and the total area equals 64cm^2
i got the answer as 0.95 and 5.05
i was wondering if 0.95 corrected to one decimal place is 1.1, since i m confused between corrct to 1 decimal place and correct to 1 significant figure

**HallsofIvy** · March 12th 2010, 11:57 AM

Originally Posted by darkpinkish

hey everybody

i couldnt figure out this question from a past paper about quadratic formula
it was pretty straight foward-
the total area of rectangle R and Q is 64cm^2
calculate the value of x correct to one decimal place
5x^2+30x+24

Surely the "past paper" you got this from must have some information about "Rectangle R and Q" and what they have to do with $5x^2+ 30x+ 24$ !

As stated they don't appear to have anything to do with one another and there is no way to find "x" with just a polynomial and not an equation.

i got 0.95 (for subtraction) and 5.05

i am jus confused on what i am suppose to choose so that the answer is 64
plus forgot what it meant by correct to one decimal place...was it rounding up?

...n also 3 significant figures....actually i m mixed up in both of them -.-

thanks

**darkpinkish** · March 12th 2010, 11:21 PM

Find ff^-1(8)

and i even want to know how is it different from f^-1(x) , the inverse

=)

**e^(i*pi)** · March 13th 2010, 05:26 AM

Originally Posted by darkpinkish

Find ff^-1(8)

and i even want to know how is it different from f^-1(x) , the inverse

=)

$ff^{-1}(8) = 8$ . This is because a function and it's inverse cancel each other out.

$ff^{-1}(x)$ means substitute the inverse of $f(x)$ into the original $f(x)$ . However, because these two are "opposite" functions the answer is always x.

See spoiler for examples:

Spoiler: