5 1/3, 5 2/3, 6. And that's about it!
Answer: The common number is 26.
Step-by-step explanation:
We know that the n-th term of a sequence is:
aₙ = 3*n^2 - 1
And the n-th term of another sequence is:
bₙ = 30 - n^2
Remember that in a sequence n is always an integer number.
We want to find a number that belongs to both sequences, then we want to find a pair of integers x and n, such that:
aₙ = bₓ
This is:
3*n^2 - 1 = 30 - x^2
Let's isolate one of the variables, i will isolate n.
3*n^2 = 30 - x^2 + 1 = 31 - x^2
n^2 = (31 - x^2)/3
n = √( (31 - x^2)/3)
Now we can try with different integer values of x, and see if n is also an integer.
if x = 1
n = √( (31 - 1^2)/3) = √10
We know that √10 is not an integer, so we need to try with another value of x.
if x = 2:
n = √( (31 - x^2)/3) = √(27/3) = √9 = 3
Then if we have x= 2, n is also an integer, n = 3.
Then we have:
a₃ = b₂
The common number between both sequences is:
a₃ = 3*(3)^2 - 1 = 26
b₂ = 30 - 2^2 = 26
This triangle is an equilateral, meaning that all the sides of the triangle are equal. We know this because all the angles of triangle are marked equal. Keeping this in mind, you can then set two of the sides equal to each other and solve for x.
3x+6=5x
6=5x-3x
6=2x
6/2=x
3=x
The answer is x=3