ElectricPavlov

Density is defined   as    mass / volume

That is the plural possessive form....you don't add another 's' in the case of a word that ends in a 's'

it means  '  products's  '        Kinda like if you were referring to the possessions of someone named Dennis...

you would type    ' All of Dennis' stuff was put in boxes'     NOT  'All of Dennis's stuff was put in boxes'

You have two different equations posted in your question....here is one

(x^8)(-x^7)  = -x^15

(9-3) / (1/3 + 1) ===  6/(1 1/3)  =  6/1  /  4/3   =    6/1 x 3/4 = 18/4 = 4 1/2

121 sqrt(3) = 121 x 1.732 = 209.578

or did you want this:

\(\sqrt[3]{121}\)  =  4.946

4/7  x  5/9  =  (4 x 5) / (9 x 7)  = 20 / 63

(x+1)^4 = 81     Take the 4th root of both side

(x+1) = +-3

x = 2 or -4

Good luck with your 'essay'  !

Happy Birthday's Eve Eve !!

To ADD fractions you have to get a 'common denominator' 

A good one in this case would be 16

1/8 + 1/16 =

2/2 (1/8) + 1/16=

2/16 + 1/16 = 3/16