Question

Докажите неравенство 3x²+12x+13>0

Answer 1

$3x {}^{2} + 12x + 13 > 0$

$3x {}^{2} + 12 x > 13 + 0$

$9 x + 12x > 13$

$21x > 13$

$x > \frac{13}{21}$