Subtract thats how you get it
Answer:
The correct answer is 15 cm.
Step-by-step explanation:
Let the width of the required poster be a cm.
We need to have a 6 cm margin at the top and a 4 cm margin at the bottom. Thus total margin combining top and bottom is 10 cm.
Similarly total margin combining both the sides is (4+4=) 8 cm.
So the required printing area of the poster is given by {( a-10 ) × ( a - 8) } 
This area is equal to 125 as per as the given problem.
∴ (a - 10) × (a - 8) = 125
⇒ 
- 18 a +80 -125 =0
⇒ - 18 a -45 = 0
⇒ (a-15) (a-3) = 0
By law of trichotomy the possible values of a are 15 and 3.
But a=3 is absurd as a 
4.
Thus the required answer is 15 cm.
The arithmetic sequence formula should help you
An= A1+ (n-1)d or An= a + d(n−1)
An= the term that you want to find.
A1 = first term in the list of ordered numbers
n = the term position (ex: for 5th term, n = 5 )
d = common difference of any pair of consecutive or adjacent numbers
So, looking the 4 choices you have the only one that follow the sequence of the formula is C
I believe the one you choose is Fibonacci sequence.
There different number of sequences:
1- arithmetic sequence
2- geometry sequence
3- Fibonacci sequence
Each of that sequences have their own formula.
So, the answer it might be C
Hope that help you
The formula for the Arithmetic is:
An = A1 + F x ( n- 1)
I believe answer is C
Because the one you chose is
Answer: (1,4)
Explanation: The domain looks at the x coordinates and (1,4) is the only x coordinate in the range given (due to the bracket)
