This is a way to factoring trinomials (there exist different equivalent methods).
Multiply the trinomial but the term accompanying . This is the second line. Then, you could take the square of the 
, ant try to create a factor () () that will correspond to the expression in the second line. That is, we want 
In ? we put the corresponding numbers that, if we multiply them we will obtain 42, and if we add them we will obtain 13. This numbers are 6 and 7. Then, we have 
The last step is divide by the number that we multipy in the first step.
The answer to this equation is 1412 or 21-15
The answer is B. Dbsjskkdjcjdks
Hello! here are the basic rules that you need to know to solve these problems:
a diameter is 2 × the radius
the circumference rule is 2×π×radius
I will solve the first question to show how to format.
1: 5/2=2.5
2×2.5×π=5×π=15.7
