2.
(5х - 4)² + (7х - 4)(7х + 4) - 74х² =
= 25х² - 40х + 16 + 49х² - 16 - 74х² = -40х,
при х = -3:
-40х = -40 * (-3) = 120,
3.
(х - 5)² - 7 = х² - 92,
х² - 10х + 25 - 7 = х² - 92,
-10х = -92 - 25 + 7,
-10х = -110,
х = 11,
3х² + 9х = 3 * (х - 6)(х + 6),
3 * (х² + 3х) = 3 * (х - 6)(х + 6),
х² + 3х = х² - 36,
3х = -36,
х = -12