x+20y+10xy=40
x+20y-10xy=-8
x+20y+10xy=40
(x+20y+10xy)-(x+20y-10xy)=40-(-8)
x+20y+10xy=40
x+20y+10xy-x-20y+10xy=40+8
x+20y+10xy=40
20xy=48
x+20y+10xy=40
xy=2.4
x+20y+24=40
xy=2.4
x+20y=16
y=2.4/x
x+20*2.4/x=16
y=2.4/x
x+48/x=16
y=2.4/x
(x+48/x)*x=16*x
y=2.4/x
x^2+48=16x
y=2.4/x
x^2-16x+48=0
y=2.4/x
(x-4)(x-12)=0
y=2.4/x
x1=4
x2=12
y1=2.4/4=0.6
y2=2.4/12=0.2
Проверка:
x1=4
y1=2.4/4=0.6
x+20y+10xy=40
4+20*0.6+10*4*0.6=40
4+12+24=40
40=40
x+20y-10xy=-8
4+20*0.6-10*4*0.6=-8
4+12-24=-8
-8=-8
x2=12
y2=2.4/12=0.2
x+20y+10xy=40
12+20*0.2+10*12*0.2=40
12+4+24=40
40=40
x+20y-10xy=-8
12+4-24=-8
-8=-8
Объяснение:
Записать в стандартном виде
400000 = 4*10^5
23000 = 2,3*10^4
8760000 = 8,76*10^6
1230 = 1,23*10^3
43 = 4,3*10^1
0,00008 = 8*10^-5
0,0076 = 7,6*10^-3
0,098 = 9,8*10^-2
0,54 = 5,4*10^-1
0,1 = 1*10^-1
7000000 = 7*10^6
560000 = 5,6*10^5
2130000 = 2,13*10^6
19700 = 1,97*10^4
51 = 5,1*10^1
0,0007 = 7*10^-4
0,00678 = 6,78*10^-3
0,042 = 4,2*10^-2
0,34 = 3,4*10^-1
0,9 = 9*10^-1
Записать в виде натурального числа или десятичной дроби:
5 ∙ 106 = 5000000
2,7 ∙ 103 = 2700
1,56 ∙ 104 = 15600
6,78 ∙ 102 = 678
3 ∙ 10-6 = 0,000003
1,2 ∙ 10-4 = 0,00012
4,76 ∙ 10-3 = 0,00476
2,3 ∙ 10-1 = 0,23
2 ∙ 105 = 200000
7,7 ∙ 104 = 77000
5,86 ∙ 105 = 586000
2,18 ∙ 103 = 2180
4 ∙ 10-5 = 0,00004
7,2 ∙ 10-5 = 0,000072
6,12 ∙ 10-2 = 0,0612
6,5 ∙ 10-1 = 0,65
