Answer
Explicit formula; an = -3 + (n-1)(8)
25th term = 189
Explanation:
Given the sequence
-3, 5, 13, 21 ....
The formula for calculating the nth term of the sequence is expressed as;
an = a + (n-1)d
a is the first term
n is the number of terms
d is the common difference
Given
a = -3
d = 5-(-3) = 13 - 5 = 8
Substitute the values into the formula
an = -3 + (n-1)*8
Hence the explicit formula is expressed as an = -3 + (n-1)(8)
To get the 25th term, you will substitute n = 25 into the explicit formula as shown;
a25 = -3 + (25-1)(8)
a25 = -3+(24)(8)
a25 = -3 + 192
a25 = 189
Hence the 25th term will be 189
