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Saturday, September 2, 2017

2017/022) Solve (2x+1)(30x+1)(3x+1)(5x+1) = 10

we have (2x+1)(30x+1)(3x+1)(5x+1) = 10
or
(60x^2+ 32x + 1)(15x^2+ 8x + 1) = 10

letting 15x^2 + 8x = t
(4t+1)(t+1) = 10
or
4t^2 + 5 t + 1 = 10
or 4t^2 + 5t - 9 = 0
or (4t+9)(t-1) = 0

t =  1 or -9/4
t = 1 gives
15x^2 + 8x-1=0 giving x = \dfrac{-4\pm\sqrt{31}}{15}

or  (15x^2 + 8x +\frac{9}4{4}) = 0
or (60x^2+ 32x + 9) = 0
this gives complex solution
so solutions are  x = \dfrac{-4\pm\sqrt{31}}{15}

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