What is the following simplified product assume x > 0

The answer 

the full question is as following:
What is the following simplified product assume x >0
and 2√8x^3  (3√10x^4 - x√5x²) 
let A(x)=2√8x^3  (3√10x^4 - x√5x²) 
the main rules are: 
√a²= a,  for all value positive of a

it was assumed that x >0
so,

√8x^3 = √8√x^3 =√(4x2) √(x x²)  = (2√2)x√x, because √x²=x
√10x^4 = x²√10, because √x^4=√x²x²=x*x=x²
x√5x²) = x²√5, because √5x²= x√5

therefore, 
A(x)=2√8x^3  (3√10x^4 - x√5x²) = 2*(2√2)x√x(3x²√10 - x²√5)
and (3x²√10 - x²√5) =x²(3√10 - √5), we get 

=4√2)x^3√x(3√10 - √5)

finally  A(x) = 4√2)(3√10 - √5) x^3√x

Answer: d. 39 cmin the diagram, the approximate length of the minor arc de is 39 centimetres.step-by-step explanation: the formula for the length of an arc in a circle is as displayed below.let the length of the minor arc de = xx = 2( pi )r × angle of sector / 360°from this, we will substitute the values given from the problem into the formula to obtain the length of the minor arc de.x = 2( pi )r × angle of sector / 360°r = radius = 25cmpi as an approximate value = 3.14angle of sector = 120°x = 2( 3.14 )( 25 ) × 120° / 360°x = 157 × 1 / 4x = 39.25x = 39 ( rounded to the nearest whole number as an approximate value )