(3/2-2/3)х=30
5х/6=30
х=180/5
<span>х=36</span>
1,2х≥7
х≥7:1,2
х≥70/12
х≥5 5/6
х∈[5 5/6;+∞)
log₄11=x
log₁₁64=log₁₁4³=3*log₁₁4=3/log₄11=3/x.
1) <span>7/9-47/72 = 56/72 - 47/72 = 8/72 = 1/8
2) 1/8 : 1,25 = 1/10
3) 1/10 + 7/40 = 4/40 + 7/40 = 11/40
4) </span><span>0,358-0,108 = 0,25 = 1/4
5) 11/40 : 1/4 = 44/40 = 11/10
6) 11/10 * 1,6 = 176/100
7) 176/100 - 19/25 = 176/100 - 19*4/100 = (176 - 76)/100 = 100/100 = 1.
Ответ: 1.</span>
Решение:
(а² + 49 - 14а)/(а² - 49) = (а - 7)²/(а - 7)•(а + 7) = (а - 7)/(а + 7)
Если а = 13, то (13-7)/(13+7) = 6/20 = 3/10= 0,3.
Ответ: 0,3.