5x^2+x=4

можно решение

5x^2 + x = 4,

5x^2 + x - 4 = 0,

D = b² - 4ac = 1² - 4 * 5 * (-4) = 1 + 4 * 5 * 4 = 1 + 80 = 81, D>0,

"/" - деление

x1 = - B + √D / 2a = - 1 + √81 / 2 * 5 = - 1 + √81 / 10 = - 1 + 9 / 10 = 4 / 5

x2 = - B - √D / 2a = - 1 - 9 / 10 = - 1.

x1 = 4/5

x2 = - 1.

Ответ: 4/5, - 1.