Mathematics: Post your doubts here!

Anika Raisa

Anika Raisa

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SararaIH said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_w09_qp_32.pdf
I need help with Q2.i) and Q6.i) PLEEAASSEE!
Click to expand...

2.i) Let f(x)=x^3-8x-13
By trial n error
(as in take values of x= 0 to any no. as long as u dont get two a positive value; u may Consider decimals too sometimes)

so i found for x=3 we get a negative value which is -10
And for x=4 we get a positive valu which id 19
so as the values have different signs the root lies betwn x=3 n x=4

Hope u got this!

Btwn working on 6 i .... gotta wait!!
 
A

aalisher

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[/COLOR said:
Rutzaba]light is abt to go...
try making factors of dnominator
2x^2 +5x+2
(1+2x)(x+2)
do partial fractions
integrate
Click to expand...


I just don't get why there are 3 terms instead of 2?
 
SararaIH

SararaIH

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Anika Raisa said:
2.i) Let f(x)=x^3-8x-13
By trial n error
(as in take values of x= 0 to any no. as long as u dont get two a positive value; u may Consider decimals too sometimes)

so i found for x=3 we get a negative value which is -10
And for x=4 we get a positive valu which id 19
so as the values have different signs the root lies betwn x=3 n x=4

Hope u got this!

Btwn working on 6 i .... gotta wait!!
Click to expand...

I don't understand one thing. I mean, how do you know which value of x is the correct value? Because even if I take x=2, I get a negative value of -21.
And even if I take x=5, I get a positive value of 72. So how do I know which value of x to consider? :(
 
Anika Raisa

Anika Raisa

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SararaIH said:
I don't understand one thing. I mean, how do you know which value of x is the correct value? Because even if I take x=2, I get a negative value of -21.
And even if I take x=5, I get a positive value of 72. So how do I know which value of x to consider? :(
Click to expand...

yes i knw that is confusing... Bt wat u do is start from zero n go serially n if u get two different signs consecutively those are the two values of x! like over here u cud have said x lies betwn 0 to 5 but to be precise u have to say 3 to 4.
U c 4 x=3 u get positive value n for x=4 u get negative so they u get different values consequentially so the root lies betwn this two...
Umm cud i make the point? :~

Btwn i also told u the procedure of 6i ! c inbox!!!
 
SararaIH

SararaIH

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Anika Raisa said:
yes i knw that is confusing... Bt wat u do is start from zero n go serially n if u get two different signs consecutively those are the two values of x! like over here u cud have said x lies betwn 0 to 5 but to be precise u have to say 3 to 4.
U c 4 x=3 u get positive value n for x=4 u get negative so they u get different values consequentially so the root lies betwn this two...
Umm cud i make the point? :~

Btwn i also told u the procedure of 6i ! c inbox!!!
Click to expand...
Oh okay :) Thanks!
 
Anika Raisa

Anika Raisa

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Hey SararaIH

Here is the soln to 6 i ... ar hah xcuse ma handwriting.... :D :cautious:

GEDC8091.JPG
SararaIH said:
I don't understand one thing. I mean, how do you know which value of x is the correct value? Because even if I take x=2, I get a negative value of -21.
And even if I take x=5, I get a positive value of 72. So how do I know which value of x to consider? :(
Click to expand...
 
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