Given: 2.25≤2+2n+2≤202
We isolate the exponential term:
0.25≤2n+2≤200
Key insight: 0.25=41=221=2−2
So our inequality becomes:
2−2≤2n+2≤200
For the left inequality: 2−2≤2n+2
Since the exponential function 2x is increasing, we can compare exponents directly:
−2≤n+2
Therefore: n≥−4
For the right inequality: 2n+2≤200
We need: n+2≤log2(200)
Since 27=128<200<256=28, we have 7<log2(200)<8
More precisely, log2(200)≈7.64
Since we need integers, n+2≤7, so n≤5
Therefore: −4≤n≤5
This means n∈{−4,−3,−2,−1,0,1,2,3,4,5}
We calculate 3+3n+1 for each value of n:
| n | n+1 | 3n+1 | 3+3n+1 | Integer? |
|---|
| -4 | -3 | 271 | 3+271=2782 | No |
| -3 | -2 | 91 | 3+91=928 | No |
| -2 | -1 | 31 | 3+31=310 | No |
| -1 | 0 | 1 | 3+1=4 | Yes |
| 0 | 1 | 3 | 3+3=6 | Yes |
| 1 | 2 | 9 | 3+9=12 | Yes |
| 2 | 3 | 27 | 3+27=30 | Yes |
| 3 | 4 | 81 | 3+81=84 | Yes |
| 4 | 5 | 243 | 3+243=246 | Yes |
| 5 | 6 | 729 | 3+729=732 | Yes |
The integer values of 3+3n+1 are: {4,6,12,30,84,246,732}