x 5 + x + 3 2 = x + 1 4 + x + 2 3
Find the sum of all real roots of x in this quadratic equation.
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x 5 + x + 3 2 = x ( x + 3 ) 5 ( x + 3 ) + 2 x = x 2 + 3 x 5 x + 1 5 + 2 x = x 2 + 3 x 7 x + 1 5 = ( 7 x + 1 5 ) ( x 2 + 3 x + 2 ) = 7 x 3 + 3 6 x 2 + 5 9 x + 3 0 = 4 x 2 + 2 6 x + 3 0 = 2 x 2 + 1 3 x + 1 5 = ( 2 x + 3 ) ( x + 5 ) = x = x + 1 4 + x + 2 3 ( x + 1 ) ( x + 2 ) 4 ( x + 2 ) + 3 ( x + 1 ) x 2 + 3 x + 2 4 x + 8 + 3 x + 3 x 2 + 3 x + 2 7 x + 1 1 ( 7 x + 1 1 ) ( x 2 + 3 x ) 7 x 3 + 3 2 x 2 + 3 3 x 0 0 0 − 2 3 , − 5
Thus, sum of all roots in above equation is ( − 2 3 ) + ( − 5 ) = − 2 1 3 = 6 . 5
If you find a common denominator for both sides of the equation, you're left with
(7x+15)/(x*(x+3)) = (7x+11)/((x+1)(x+2)) Cross multiplying: 7x^3 +32x^2+33x=7x^3+36x^2+59x+30 32x^2 +33x = 36x^2+59x+30 4x^2+26x+30=0 Quadratic formula : = (-26+/- sqrt(26^2-4(4)(30))/(2(4)) (-26 +/- sqrt(676-480))/(8) (-26 +/- 14)/(8) (-13+/- 7)/4 There are only two solutions to a quadratic ---> x = -3/2, -5
-10/2 - 3/2 = -13/2 = -6.5
From solving above equation we get, 4x^2 + 26x + 30 = 0 so by applying vieta's formula we get sum of all real roots of this equation, i.e. -26/4 = -6.5
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x 5 + x + 3 2 = x + 1 4 + x + 2 3
( x 5 + 1 ) + ( x + 3 2 + 1 ) = ( x + 1 4 + 1 ) + ( x + 2 3 + 1 )
x 5 + x + x + 3 5 + x = x + 1 5 + x + x + 2 5 + x
( 5 + x ) ( x 1 + x + 3 1 − x + 1 1 − x + 2 1 ) = 0
⇒ 5 + x = 0 or x 1 + x + 3 1 − x + 1 1 − x + 2 1 = 0
1 s t term
5 + x = 0 ⇒ x = − 5
2 n d term
x 1 + x + 3 1 − x + 1 1 − x + 2 1 = 0
x ( x + 3 ) 2 x + 3 = ( x + 1 ) ( x + 2 ) 2 x + 3
( 2 x + 3 ) ( x 2 + 3 x 1 − x 2 + 3 x + 2 1 ) = 0
⇒ 2 x + 3 = 0 ⇒ x = − 2 3 or x 2 + 3 x 1 − x 2 + 3 x + 2 1 = 0
Therefore, the sum of all real roots are − 5 + ( − 2 3 ) = − 6 . 5