Решение
4х+31√х+42=0
4(√x)∧2 + 31√x + 42 = 0
Пусть √х = у, тогда
4(у∧2)∧2 + 31у + 42 = 0
D = (31)∧2 - 4*4*42 = 961 - 672 = 289
y1 = (-31 - 17)/8 = 48 / 8 = 6
y2 = (-31+ 17)/8 = -14/8 = - 7/4
√x = 6
(√x)∧2 = (6)∧2
x1 = 36
√x = (-7/4)
(√x)∧2 = (-7/4)
x2 = 49/16
x2 = 2 13/16