5√13*2√3*√13*√3=5*13*2*3=390
.........................
5у^2-6у+1=0
Д=-6^2-4*5*1=16
√16=4
Х1=-в+√д/2а=6+4/10=1
Х2=6-4/10=-5
<span>8,4х+3-5(7,2х+0,3) = 8,4х+3 -36х -1,5= -27,6х +1,5</span>
<span>при х = 2/3</span>
<span>-27,6 х 2/3 +1,5 = -27 6/10 х 2/3 + 1 5/10= - 27 3/5 х 2/3 +1 1/2= -138/5 х 2/3 +3/2= -92/5 +3/2 = (-184 +15)/10 = -169/10= -16,9</span>