Q. Find the sum of the first 8 terms of the following series, to the nearest integer.3,4,316,…Answer:
Determine Series Type: To find the sum of the first 8 terms of the series, we first need to determine if the series is arithmetic or geometric. We can do this by examining the relationship between consecutive terms.
Identify Common Ratio: The second term is 4, which is 1 more than the first term, 3. However, the third term is 316, which is not obtained by adding or subtracting the same value from the second term. Instead, it seems that each term is being multiplied by a common ratio to get the next term. To confirm this, let's find the ratio between the second and first term, and between the third and second term.
Apply Sum Formula: The ratio between the second and first term is 34. The ratio between the third and second term is (316)/4=34. Since the ratio is consistent, this is a geometric series with a common ratio of 34.
Calculate (34)8: Now that we know it's a geometric series, we can use the formula for the sum of the first n terms of a geometric series, which is Sn=(1−r)a(1−rn), where a is the first term, r is the common ratio, and n is the number of terms.
Substitute Values: Let's plug in the values we know: a=3, r=34, and n=8. So, S8=3(1−(34)8)/(1−34).
Simplify Expression: First, we calculate (34)8. This is a calculation that typically requires a calculator, as it involves raising a fraction to a high power.
Perform Subtraction: After calculating (34)8, we get approximately 656165536. Now we can substitute this value back into the sum formula.
Multiply by −9: Now we have S8=3(1−65536/6561)/(1−4/3). Since 1−4/3 is −1/3, we can simplify the denominator to −1/3.
Round to Nearest Integer: Simplifying the expression, we get S8=3(1−656165536)×(−3)=−9(656165536−1).
Round to Nearest Integer: Simplifying the expression, we get S8=3(1−656165536)×(−3)=−9(656165536−1).We need to subtract 1 from 656165536, which gives us 656165536−65616561=656165536−6561.
Round to Nearest Integer: Simplifying the expression, we get S8=3(1−656165536)×(−3)=−9(656165536−1).We need to subtract 1 from 656165536, which gives us 656165536−65616561=656165536−6561.After performing the subtraction, we get 656165536−6561=656158975. Now we can multiply this by −9 to get the sum of the first 8 terms.
Round to Nearest Integer: Simplifying the expression, we get S8=3(1−656165536)×(−3)=−9(656165536−1).We need to subtract 1 from 656165536, which gives us 656165536−65616561=656165536−6561.After performing the subtraction, we get 656165536−6561=656158975. Now we can multiply this by −9 to get the sum of the first 8 terms.Multiplying −9 by 656158975 gives us −6561530775. This is the exact sum of the first 8 terms, but we need to round it to the nearest integer.
Round to Nearest Integer: Simplifying the expression, we get S8=3(1−656165536)×(−3)=−9(656165536−1).We need to subtract 1 from 656165536, which gives us 656165536−65616561=656165536−6561.After performing the subtraction, we get 656165536−6561=656158975. Now we can multiply this by −9 to get the sum of the first 8 terms.Multiplying −9 by 656158975 gives us −6561530775. This is the exact sum of the first 8 terms, but we need to round it to the nearest integer.Dividing 11 by 12 gives us approximately 13. Rounding this to the nearest integer gives us 14.
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