Докажите неравенство (c-5)(c+2)≥3c(3-c)-19

Question

Докажите неравенство (c-5)(c+2)≥3c(3-c)-19

Answer 1

(c-5)(c+2)≥3c(3-c)-19
с^2+2c-5c-10≥9c^2-3c^2-19
c^2-3c-10≥6c^2-19
c^2-3c-6c^2≥-19+10
-5c^2-3c+9≥0