Вправи: 486

486. Розв’яжи рівняння.

a) (x – 4)² = x(x + 8);

x² – 8x + 16 = x² + 8x;

–8x – 8x = –16;

–16x = –16|: (–16);

x = 1.

б) (5 – 2y)² = 4y² + 65;

25 – 20y + 4y² = 4y² + 65;

–20y = 65 – 25;

–20y = 40|: (–20);

y = –2.

в) (x + 7)² – x² = 3(5x + 15);

x² + 14x + 49 – x² = 15x + 45;

14x – 15x = 45 – 49;

–x = –4|: (–1);

x = 4.

г) (x – 3)(x – 4) – (x – 5)² = –10;

x² – 4x – 3x + 12 – x² + 10x – 25 = –10;

3x = –10 + 13;

3x = 3;

x = 1.