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Algebra Level pending

The sum of all distinct integral solutions of the equation:( 2x^4-9x^3+14x^2-9x+2)=0 is?


The answer is 3.

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2 solutions

Maggie Miller
Aug 3, 2015

2 x 4 9 x 3 + 14 x 2 9 x + 2 = ( x 1 ) 2 ( 2 x 1 ) ( x 2 ) 2x^4-9x^3+14x^2-9x+2=(x-1)^2(2x-1)(x-2) . Therefore, the distinct integer roots are 1 1 and 2 2 , so the answer is 3 \boxed{3} .

The sum of coefficients is 0 0 . Hence it can be inferred that x = 1 x = 1 is one of the roots.

By using Synthetic Division, we get

2 x 4 9 x 3 + 14 x 2 9 x + 2 = ( x 1 ) ( 2 x 3 7 x 2 + 7 x 2 ) = ( x 1 ) ( p ( x ) ) 2x^4 - 9x^3 + 14x^2 - 9x + 2 = (x-1)(2x^3 - 7x^2 + 7x - 2) = (x-1)(p(x))

The sum of coefficients of p ( x ) p(x) is also 0 0 . Hence, x = 1 x =1 is a root of p ( x ) p(x) as well as of the original given polynomial.

Again by Synthetic Division,

2 x 4 9 x 3 + 14 x 2 9 x + 2 = ( x 1 ) ( x 1 ) ( 2 x 2 5 x + 2 ) = ( x 1 ) 2 ( 2 x 2 5 x + 2 ) 2x^4 - 9x^3 + 14x^2 - 9x + 2 = (x-1)(x-1)(2x^2 - 5x + 2) = (x-1)^2 (2x^2 - 5x + 2)

2 x 2 5 x + 2 = 2 x 2 4 x x + 2 = 2 x ( x 2 ) 1 ( x 2 ) = ( 2 x 1 ) ( x 2 ) \Rightarrow 2x^2 - 5x + 2 = 2x^2 - 4x - x + 2 = 2x(x-2) -1(x-2) = (2x-1)(x-2)

2 x 4 9 x 3 + 14 x 2 9 x + 2 = ( x 1 ) 2 ( 2 x 1 ) ( x 2 ) \Rightarrow 2x^4 - 9x^3 + 14x^2 - 9x + 2 = (x-1)^2(2x-1)(x-2)

Sum of the distinct roots is 3 \color{#3D99F6}{\boxed{3}} .

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