2,3
390
6,5 ...........................
1 мин = 60 с
228 = 3*60 + 48 = 3 мин 48 с = 3,8 мин
Ответ: 3,8 мин
1265
(6;1) и (6;5) или (-2;1) и (-2; 5)
<span>1) 2х-5=х+1
2х-х=1+5
х=6
2) </span><span>3(х-5)=х+3
3х-15=х+3
3х-х=3+15
2х=18
х=9
3) </span><span>7(х+6)=4(5х+4)
7х+42=20х+16
7х-20х=16-42
-13х=-26
13х=26
х=2
4) </span><span>1,5(х+8)=-4х+1
1,5х+12=-4х+1
1,5х+4х=1-12
5,5х=-11
х= - 2
5) </span><span>1/6(х+9)=-1/3х
1/6x+9/6=-1/3x
1/6x+1/3x=-9/6
1/6x+2/6x=-3/2
3/6x=-3/2
1/3x=-3/2
x=-3/2:1/3=-3*3/2*1=-6/2
x= -3
</span>
<span>6) 3/4(х+8)=2х+1
3/4x+3*8/4=2x+1
3/4x-2x=1-6
3/4x-8/4x=-5
-5/4x=-5
</span><span><span>5/4x=5
x=5:5/4=5*4/5
х=4
</span></span>