Answer:
C) 12.2 cm
Step-by-step explanation:
To find the area of a square, you multiply length and width, which for a square, are the same. So to find the length of one of its sides, you have to take the square root of the area.

4b²+20b+25=0
Divide everything by 4
b²+5b+ 6.25=0
use the quadratic formula
x= (-b+ or - √b²-4ac) /2a
x= (-5 + or - √5²-4*1*6.25) /2(1)
x= -5/2 so
in this case, b= -5/2
The answer is actually D. The limit on the left side is computing the derivative at x = a. The right side value of 7 tells us that f ' (a) = 7