Answer:
x=2, x=-2
Step-by-step explanation:
3x²-3+4x²-12=13
7x²=13+12+3
7x²=28
x²=4
x=-2
x=2
The formula is 
What are series?
In mathematics, we can describe a series as adding infinitely many numbers or quantities to a given starting number or amount.
We will find the formula as shown as below:
Let 
We know 



.
.

On adding










Hence, the formula is 
Learn more about Series here:
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Answer: Cross section
Step-by-step explanation: A cross section sounds just like what it is. It’s a plane that intersects a solid figure. A cross section can happen on any solid figure.