Решите неравенство x²-20x≥-11x-7-x²

Question

Решите неравенство x²-20x≥-11x-7-x²

Answer 1

X²-20x+11x+7+x²≥0
2x²-9x+7≥0
D=81-56=25
x1=(9-5)/4=1
x2=(9+5)/4=3,5
x∈(-∞;1] U [3,5;∞)