1) p² + 4b² = (p² + 4pb + 4b²) - 4pb = (p + 2b)² - 4pb = 8² - 4 · 10 = 64 - 40 = 24
<span>А) sin 80 cos 21 – cos 81 sin 21=sin(81-21)=sin60=V3/2</span>