Monday, November 22, 2010

Given the fraction E(x)=(x^3-3x-2)/(x^3+1+3x^2+3x). Solve the equation E(x)=square root 3-square root 2.

We'll re-write the numerator
as:


x^3 - 3x - 2 = x^3 - x - 2x -
2


We'll factorize the first 2 terms and the last 2
terms:


x^3 - x - 2x - 2 = x(x^2 - 1) - 2(x +
1)


The difference of squares x^2 - 1 = (x - 1)(x +
1)


x^3 - x - 2x - 2 = x(x - 1)(x + 1) - 2(x +
1)


We'll factorize again by (x +
1):


x^3 - x - 2x - 2 = (x + 1)[x(x+1) -
2]


x^3 - x - 2x - 2 = (x + 1)(x^2 + x -
2)


The roots of the quadratic x^2 + x - 2 are - 1 and
2.


x^3 - x - 2x - 2 = (x +
1)(x+1)(x-2)


We'll re-write the denominator
as:


(x^3+1)+(3x^2+3x)


We'll
re-write the difference of cubes and we'll factorize the last 2
terms:


(x+1)(x^2 - x + 1) + 3x(x + 1) = (x+1)(x^2 - x + 1 +
3x)


(x+1)(x^2 - x + 1) + 3x(x + 1) = (x+1)(x^2 + 2x +
1)


 (x+1)(x^2 + 2x + 1) = (x+1)(x+1)^2 =
(x+1)^3


We'll re-write E(x) = (x +
1)^2*(x-2)/(x+1)^3


We'll simplify and we'll
get:


E(x) = (x-2)/(x+1)


We'll
solve the equation:


(x-2)/(x+1) = sqrt3 -
sqrt2


x - 2 = (sqrt3 -
sqrt2)(x+1)


x - x(sqrt3 - sqrt2) = sqrt3 - sqrt2 +
2


x(1 - sqrt3 + sqrt2) = sqrt3 - sqrt2 +
2


x = (sqrt3 - sqrt2 + 2)/(1 - sqrt3 +
sqrt2)

No comments:

Post a Comment

Calculate tan(x-y), if sin x=1/2 and sin y=1/3. 0

We'll write the formula of the tangent of difference of 2 angles. tan (x-y) = (tan x - tan y)/(1 + tan x*tan y) ...