The 21st term of the AP whose first two terms are -3 and 4 is
a. 17
b. 137
c. 143
d. -143
Solution:
An arithmetic progression (AP) is a sequence where the two consecutive terms have the same common difference. It is obtained by adding the same fixed number to its previous term.
The nth term of an AP is
aₙ = a + (n - 1 )d.
a = first term
aₙ = nth term
d = common difference.
By the question above,
a = - 3
a₂ = 4.
Substituting values, we get,
a₂ = a + d
4 = - 3 + d
d = 7.
Considering the question,
aₙ = a + (n - 1 )d.
a₂₁ = a + 20d
a₂₁ = - 3 + (20)(7)
a₂₁ = 137.
Therefore, a₂₁ = 137.
✦ Try This: The 7th term and 10th terms of an AP are 12 and 25. Find the 12th term
☛ Also Check: NCERT Solutions for Class 10 Maths Chapter 5
NCERT Exemplar Class 10 Maths Exercise 5.1 Problem 6
The 21st term of the AP whose first two terms are -3 and 4 is, a. 17, b. 137, c. 143, d. -143
Summary:
An arithmetic progression (AP) is a sequence where the two consecutive terms have the same common difference. The 21st term of the AP whose first two terms are -3 and 4 is 137
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