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if the first term is 2 and the S5 =one forth of the sum of next 5 term then find the sumof 30 terms? |
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Answer» a=2 S5=5/2(2*2+4d) S10=10/2(2*2+9d) given S5=1/4(S10-S5) 5/2(4+4d)=5(4+9d)/4 4(1+d)=2(4+9d)/4 2+2d=4+9d/4 7d=-2/4 d=-1/14 ,A20=2+19(-1/14) =2-19/14 =9/14 |
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