1.

Thefirst two terms of a geometric progression add up to 12. The sum of the thirdand the fourth terms is 48. If the terms of the geometric progression arealternately positive and negative, then the first term is

Answer» `a,ar,ar^2,ar^3`
`a+ar=12---(1)`
`ar^2+ar^3=48 `
`r^2(a+ar)=48---(2)`
`(1)/(2)=1/r^2=1/4`
`r^2=4`
`r=+2,-2`
`r=2`
`a+ar=12`
`a(1-2)=12`
`a=-12`
option `2`is correct


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