Answer:
A. 7
Step-by-step explanation:
The answer to the variable b is 708.4
Answer:

Step-by-step explanation:
Area of the shaded region = area of the large rectangular - area of the small rectangle
Area of rectangle is given as l*w
Area of the large rectangle = 
Expand


Area of large rectangle 
Area of small rectangle = 


Area of small rectangle = 
Area of shaded region = 

Collect like terms


When the leading coefficient is 1,
If the constant ( c term) is a perfect square and the b term is 2* the square root of the c term.
Ex.
x*2 + 10x + 25
2*5 = 10 5*5=25
Ex.
x^2 - 12x + 36
2 * -6 = -12 6*6=36