1. (5x-4) (x+8) = 0 2. (a/c+c/a-2) * 1/a-c 3. разложить на множетели a^3-4a

1) (5x - 4) (x + 8) = 0;

5x - 4 = 0 или x + 8 = 0;

5x = 4;

x = 4/5 или x = - 8.

2) (a/c + c/a - 2) * 1/a - c = 1/a * a/c + 1/a * c/a + 1/a * ( - 2) - c = (1 * a) / (a * c) + (1 * c) / (a * a) - 2/a - c = 1/c + c/a² - 2/a - c = (1/c - c) + (c/a² - 2/a) = (1 - c²) / c + (c - 2a) / a²;

3) a³ - 4a = a (a² - 4) = a (a² - 2²) = a (a - 2) (a + 2).