Answer:
1)D 2)C 3)A 4)B 5) A
Step-by-step explanation:
1) The area rectangle is 36x^2 -1
 We know , 
 A= l*b
 =36x^2 -1
 =(6x)^2 -1
 =(6x+1) (6x-2)
This the value of l,b respectively.
So, Perimeter of rectangle is 2(l+b)
 P=2(6x+1) + 2(6x-1)
 =24x
2)The area of square is 4(x+5)^2
 We know,
 A=l^2
 =4(x+5)^2
 =4(x^2 + 10x + 25)
 =(2x+10)^2
This is the value of l=2x+10.
So, Perimeter of square is 4l
 P=4(2x+10)
 =8x+40
3)The fully factorized form is 
 = -2x^2 + 10x +12
 = -2x^2 + 12x -2x +12
 = -2x(x-6) -2(x-6)
 = -2(x-6) (x+1)
4)The fully factorized form is
 =x^4 -81
 =(x^2)^2 -9^2
 =(x^2 + 9) (x^2 - 9)
 =(x^2 + 9) (x^2 - 3^2)
 =(x^2 + 9) (x + 3) (x - 3)
5)The fully factorized form is 
 = 5x^4 - 320
 = 5(x^4 - 64)
 = 5((x^2)^2 - 8^2)
 = 5(x^2 + 8) (x^2-8)