Find an explicit form f(n) of the arithmetic sequence where the 2nd term is 25 and the sum of the 3rd term and 4th
1 answer:
Answer:f(n) = 12n + 1
Step-by-step explanation:
Since it is an arithmetic sequence, the general formula for nth term is given as
f(n) = a + ( n-1)d , where a is the first term, n is the number of terms and d is the common difference.
Given from the question
Second term is 25 , which means that
a + d = 25
Also given , the sum of third and fifth term is 86, which means
a + 2d + a + 3d = 86
2a + 5d = 86
Combining the two equations , we have
a + d = 25 ………….. I
2a + 5d = 86………..II
Using substitution method to solve the resulting simultaneous equation
From equation I make a the subject of the formula, which gives
a = 25 – d…………………. III
Substitute the value of a into equation II , we have
2 ( 25 – d) + 5d = 86
Expanding
50 + 2d + 5d = 86
50 + 3d = 86
Collect the like terms
3d = 86 – 50
3d = 36
d = 12
substitute the value of d into equation III, we have
a = 25 – 12
a = 13
Since we have gotten the value of a and b , we will substitute into the general formula for the nth term
f(n) = a + ( n-1)
f(n) = 13 + (n-1)12
Expanding
f(n) = 13+ 12n -12
f(n) =12n + 1
Therefore the explicit form f(n) of the arithmetic sequence is f(n) =12n + 1
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Given 2.50x + 3.50y < 30.
Where x represent the number of hamburgers and y represent the number of cheeseburgers.
Now question is to find the maximum value of hamburgers Ben could have sold when he has sold 4 cheeseburgers.
So, first step is to plug in y=4 in the given inequality. So,
2.50x+3.50(4)<30
2.50x+14 <30
2.50x<30- 14 Subtracting 14 from each sides.
2.50x< 16
Dividing each sides by 2.50.
x<6.4
Now x being number of hamburgers must be an integer , so tha maximum value of x can be 6,
thus x = 6 hamburgers
So, the maximum value of hamburgers Ben could have sold is 6*2.5=$15
Hope this helps!!