81c² - d² + 9c + d = (81c² - d²) + (9c + d) = (9c - d)(9c + d) + (9c + d) =
= (9c + d)(9c - d + 1)
<span>1/9у^2-2ху+9х^2=(1/3y)</span>²-2(1/3y)*(3x)+(3x)²=(1/3y-3x)²
<span>1)x^4-16z^4=(х^2-4z^2)(x^2+4z^2)
</span><span>2)81-k^4=(9-k^2)(9+k^2)</span>
(8p³ + 5p²q)² = (8p³)² + 2 * 8p³ * 5p²q + (5p²q)² = 64p⁶ + 80p⁵q + 25p⁴q²