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 Community Discussion Question:
Surds
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![[Post New]](/templates/default/images/icon_minipost_new.gif) 4 Jan 2008 21:26:17 IST
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Q.(15+4[ ] 14)x2-7x+11+(15-4[ ]14)x2-7x+11=30.then the no.of real values of x are?
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4 Jan 2008 21:27:51 IST
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Please note:in the above question it is x to the power of 2 and not 2x...
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Hey in these type of qs....
af(x) + bf(x) = a + b
and ab = 1.....it always give f(x) = 1 and f(x) = -1
so
x2 -7x+11 = 1 , x2 -7x + 11 = -1
now solve
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I always like to walk in rain as no one can see me crying there :(
frnds are like diamonds , if u hit them , they don't break but they slip frm ur hands
-----It is better to be hated for what you are than to be loved for what you are not.----
*****wen love and skill work together--expect a masterpiece*****
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4 Jan 2008 21:39:15 IST
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the other method
(15 + 4 root14)(15-4root14) = 225 - 224 = 1
(15 + 4root14) = 1 / (15 - 4root14)
soo
(15 + 4root14)x^2 -7x+11 + 1/ (15 + 4root14)x^2-7x+11 = 30
(15 + 4root14)x^2-7x +11 = y
y + 1/y = 30
y comes out to be
15+_4root14
now take 1ce 15 + 4root14 = (15 + 4root14)x^2-7x+11
then....try
the other 1...
cheers!
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I always like to walk in rain as no one can see me crying there :(
frnds are like diamonds , if u hit them , they don't break but they slip frm ur hands
-----It is better to be hated for what you are than to be loved for what you are not.----
*****wen love and skill work together--expect a masterpiece*****
|
this reply: 5 points
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