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Monday, August 30, 2021

2021/068) Prove that the polynomial equation x^8-x^7+x^2-x+15=0 has no real solution.

 We have x^8-x^7 + x^2 -x + 15 = x^7(x-1) + x(x-1) + 15

Each term is positive for x > 1 so LHS is greater than 0 so no solution for x > 1

For x = 1 LHS = 15 so x = 1 is not a solution

Further x^8-x^7 + x^2 -x + 15 = (15- x) + x^2(1-x^5) + x^8

Each term is positive for x < 1 so LHS is greater than 0 so no solution for x < 1

Hence no real solution

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