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\(\pi\)
e
\(\frac{a}{b}\)
!
←
→
(
)
\(\sqrt{\,}\)
\(a^{b}\)
7
8
9
\(\div\)
log
ln
4
5
6
\(\times\)
cos
cos⁻¹
1
2
3
-
sin
sin⁻¹
0
.
=
+
tan
tan⁻¹
A computer virus infects 4 computers initially. Each day, the number of infected computers quadruples.
Let \(u_n\) be the number of infected computers at day \(n\).
What are the first three terms of the sequence \((u_n)\)?
\(u_1 =\)
7
8
9
+
4
5
6
-
1
2
3
*
C
0
.
÷
computers
\(u_2 =\)
7
8
9
+
4
5
6
-
1
2
3
*
C
0
.
÷
computers
\(u_3 =\)
7
8
9
+
4
5
6
-
1
2
3
*
C
0
.
÷
computers
What is its recursive rule?
\(u_{n+1}=\)
\(\pi\)
\(e\)
\(x\)
\(n\)
\(u_n\)
\(f\)
\(\frac{a}{b}\)
\(\sqrt{\,}\)
\({a}^{b}\)
\(\ln{\,}\)
\(\log{\,}\)
!
7
8
9
←
→
\(\sin{\,}\)
4
5
6
(
)
\(\cos{\,}\)
1
2
3
\(\times\)
\(\div\)
\(\tan{\,}\)
C
0
.
+
-
=
What is its explicit rule?
\(u_{n}=\)
\(\pi\)
\(e\)
\(x\)
\(n\)
\(u_n\)
\(f\)
\(\frac{a}{b}\)
\(\sqrt{\,}\)
\({a}^{b}\)
\(\ln{\,}\)
\(\log{\,}\)
!
7
8
9
←
→
\(\sin{\,}\)
4
5
6
(
)
\(\cos{\,}\)
1
2
3
\(\times\)
\(\div\)
\(\tan{\,}\)
C
0
.
+
-
=
How many computers will be infected after 10 days?
\(u_{10}=\)
7
8
9
+
4
5
6
-
1
2
3
*
C
0
.
÷
computers
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