an=4 ,d=2, sn=-14 find \'n\' and \'a\' .

1.	an=4 ,d=2, sn=-14 find \'n\' and \'a\' .
Answer» an=4a+(n-1)d=4a+2n-2=4a+2n=6a=6-2n-------(1)Sn=-14n/2(2a+(n-1)d)=-14n/2(2a+(n-1)2)=-14n(a+n-1)=-14n(6-2n+n-1)=-14-----from (1)n(5-n)=-145n-n²=-14n²-5n-14=0n²-(7-2)n-14=0n²-7n+2n-14=0n(n-7)+2(n-7)=0(n+2)(n-7)=0Therefore, n=7Putting the value of n in equation (1)a=6-2×7a=6-14a=-8

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