Вправа 651 алгебра Бевз гдз 7 клас
№ 651
- a) x2(x2 + 4x + 4) = (5x)2 + 100x + 100
x4 + 4x3 + 4x2 = 25x2 + 100x + 100
x3(x + 4) – 25x(x + 4) + 4x2 – 100 = 0
(x + 4)(x3 – 25x) + 4(x2 – 25) = 0
(x + 4) • x(x2 – 25) + 4(x2 – 25) = 0
(x2 – 25)((x + 4) • x + 4) = 0
(x2 + 25)(x2 + 4x + 4) = 0
(x2 – 25)(x + 2)2 = 0
x1 = –5; х2 = 5; х3 = –2;
б) 4x4 – 12x3 + 9x2 = 36x2 – 108х + 81
х2(4х2 – 12х + 9) = 36х2 – 108х + 81
х2 • (2х – 3)2 = (6х – 9)2
х2 • (2х – 3)2 – 9(2х – 3)2 = 0
(2х – 3)2 • (х2 – 9) = 0
х1 = 1,5; х2 = –3; х3 = 3.
вправи поруч
