Question

3. किसी स. श्रे. में
(i) t3 = 15, S10 =125 तो d और t10 निकालें।
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Answer 1

Step-by-step explanation:

t3 = A3 = a + 2d = 15

a = 15 - 2d -------(1)

S(10) = 125

10/2 { 2a + 9d } = 125

5 { 2a + 9d } = 125

2a + 9d = 25 ------(2)

from equation (1) & (2)

2(15 - 2d) + 9d = 25

30 - 4d + 9d = 25

5d = -5

d = -1

a = 15 - 2(-1) = 15 + 2 = 17

t10 = A(10) = a + 9d

= 17 + 9(-1)

= 17 - 9 = 8