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eissa

eissa

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eissa
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  • Sn=n/2*{2a+(n-1)d} where S is the sum , n is the number of terms , a is the first term, d is the difference S20= 20/2*{2a+(20-1)d}=540 so ==> 540=10(2a+19d) divide by 10 so 2a+19d=54 ...........(1) S30=30/2 *{2a+(30-1)…
  • Sn=n/2*{2a+(n-1)d} where S is the sum , n is the number of terms , a is the first term, d is the difference S20= 20/2*{2a+(20-1)d}=540 so ==> 540=10(2a+19d) divide by 10 so 2a+19d=54 ...........(1) S30=30/2 *{2a+(30-1)…
  • Sn=n/2*{2a+(n-1)d} where S is the sum , n is the number of terms , a is the first term, d is the difference S20= 20/2*{2a+(20-1)d}=540 so ==> 540=10(2a+19d) divide by 10 so 2a+19d=54 ...........(1) S30=30/2 *{2a+(30-1)…
  • Sn=n/2*{2a+(n-1)d} where S is the sum , n is the number of terms , a is the first term, d is the difference S20= 20/2*{2a+(20-1)d}=540 so ==> 540=10(2a+19d) divide by 10 so 2a+19d=54 ...........(1) S30=30/2 *{2a+(30-1)…
  • Sn=n/2*{2a+(n-1)d} where S is the sum , n is the number of terms , a is the first term, d is the difference S20= 20/2*{2a+(20-1)d}=540 so ==> 540=10(2a+19d) divide by 10 so 2a+19d=54 ...........(1) S30=30/2 *{2a+(30-1)…
  • Sn=n/2*{2a+(n-1)d} where S is the sum , n is the number of terms , a is the first term, d is the difference S20= 20/2*{2a+(20-1)d}=540 so ==> 540=10(2a+19d) divide by 10 so 2a+19d=54 ...........(1) S30=30/2 *{2a+(30-1)…