Question

The A.P. in which 4th term is -15 and 9th term is -30. Find the sum of the first 10

numbers.​

Answer 1

Answer:

S₁₀=765

Step-by-step explanation:

 a+8d=-30

-(a+3d=-15)

5d=-15

d=-3

a+8d=-30

a +8*-15=-30

a-120=-30

a= 120-30

a=90

$S_{n}$= n/2(2a+(n-1)d)

S₁₀= 10/2 (2*90+9*-3)

S₁₀= 10/2(180-27)

S₁₀=5*153

S₁₀=765

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