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| 1. |
The first term of a GP is 1.If the sum of 3rd and 5th term is 90.Find the common ratio of GP |
| Answer» Given a=1 , ar²+ar⁴=90ar²(1+r²)=901r²(1+r²)=90Let r²= yy(1+y)=90y²+y-90=0y²+10y-9y-90=0y(y+10)-9(y+10)=0(y-9)(y+10)=0Changing y by r²(r²-9)(r²+10)=0(r²+10) is an imaginary number so neglect itr²=9r=3 | |