Need some helps!

Find the value of xx:
x2x^2 + (xx1\frac {x} {x-1})2^2 = 54\frac {5} {4}

Note by Mục Xiên
4 years, 9 months ago

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I expanded it, and by hit and trial method, -1 was the solution. Then I divided the expanded polynomial by (x+1). The resultant cubic can be easily factorised.

Ninad Jadkar - 4 years, 9 months ago

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x=y+1 x = y + 1

(y+1)2+(y+1y)2=54 ( y + 1)^2 + (\dfrac{y + 1}{y})^2 = \dfrac{5}{4}

y2+2y+1+1+1y2+2y=54 y^2 + 2y + 1 + 1 + \dfrac{1}{y^2} + \dfrac{2}{y} = \dfrac{5}{4}

y2+1y2+2y+2y+2=54 y^2 + \dfrac{1}{y^2} + 2y + \dfrac{2}{y} + 2 = \dfrac{5}{4}

a=y+1y a = y + \dfrac{1}{y}

a22+2a+2=54 a^2 - 2 + 2a + 2 = \dfrac{5}{4}

(a+1)2=(±32)2 (a + 1)^2 = (\pm \dfrac{3}{2})^2

a=52,12 a = - \dfrac{5}{2} , \dfrac{1}{2}

y+1y=52,y+1y=12 y + \dfrac{1}{y} = - \dfrac{5}{2} , y + \dfrac{1}{y} = \dfrac{1}{2}

y=52±942,y=12±i1542 y = \dfrac{ -\dfrac{5}{2} \pm \sqrt{\dfrac{9}{4}}}{2} , y = \dfrac{ \dfrac{1}{2} \pm i\sqrt{\dfrac{15}{4}}}{2}

x1=52±942,x1=12±i1542 x - 1 = \dfrac{ -\dfrac{5}{2} \pm \sqrt{\dfrac{9}{4}}}{2} , x - 1 = \dfrac{ \dfrac{1}{2} \pm i\sqrt{\dfrac{15}{4}}}{2}

(x1=12,4) or x1=12±i1542 (x - 1= \dfrac{-1}{2} , -4) ~or~ x - 1 = \dfrac{ \dfrac{1}{2} \pm i\sqrt{\dfrac{15}{4}}}{2}

x=12,3,3±i154 x = \dfrac{1}{2} , -3 , \dfrac{3 \pm i\sqrt{15}}{4}

U Z - 4 years, 9 months ago

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x= -1 or 1/2

Ninad Jadkar - 4 years, 9 months ago

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Can I know how to solve this, please?

Mục Xiên - 4 years, 9 months ago

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What have you tried?

Do you know how to clear denominators and factorize?

Calvin Lin Staff - 4 years, 9 months ago

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@Calvin Lin I've already cleared denominators and got
4x24x^2 - 8x38x^3 + 3x23x^2 + 10x10x - 55 = 00
What to do next?

Mục Xiên - 4 years, 9 months ago

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@Mục Xiên well, we want to start to factorize the polynomial. You can use the rational root theorem
to guess at possible roots, and after which use the remainder factor theorem to help factorize. Have you seen these theorems before?

Calvin Lin Staff - 4 years, 9 months ago

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@Calvin Lin Well, I think I haven't seen these theorems before. Because I'm a middle school students. BTW, I'll ask my teacher for this problem's explaination, thanks for your helps!

Mục Xiên - 4 years, 9 months ago

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