Question

the sum of 1st five term of Ap is 40 and the sum of next five term is 90 find the value of 1st term​

Answer 1

Answer:

first term=4

Step-by-step explanation:

S₅=40

S₁₀-S₅=90

S₅=5/2[2a+(5-1)d]

2a+4d=40*2/5

2a+4d=16.................(1)

S₁₀-S₅=90

S₁₀=90+S₅

S₁₀=90+40

S₁₀=130

S₁₀=10/2[2a+(10-1)d]

2a+9d=130/5

2a+9d=26...........(2)

eq2-eq1=>

    2a+9d=26

-    2a+4d=16

     0+ 5d =10

            d=2

substitute d=2 in eq1

2a+4(2)=16

2a=16-8

a=8/2

a=4

first term=4

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