The number of people who spread in the first round =1* x = X. The total number of patients became1+X.
Number of new infections in the second round =( 1+x)*x Only those infected in the second round will be added to the original number.
Total population = x * (x+1)+x+1=100.
(x+ 1)^2= 100
x=9
2) solution: let the average annual growth rate of per capita income be x.
[There are two years from 20065438+0 to 2003]
1200*( 1+x)^2= 1452
(1+x)2 = 1.25438+0[ simultaneous extraction on both sides]
1+X=+ - 1. 1
X 1=0. 1
X2=-2. 1 (irrelevant, omitted)
0. 1= 10%
A: The average annual growth rate of per capita income is 10%.
3)
* * * There are X companies participating.
x(x- 1)/2=45
x^2-x-90=0
(x- 10)(x+9)=0
X= 10 or x=-9 (omitted)
A: * * * There are 10 companies involved.