X sqrt 5xy^4 + sqrt 405x^3y^4-sqrt 80x^3y^4

the three terms can be combined and reduce to:

Step-by-step explanation:

Start by extracting all perfect square factors from the square root in order to simplify the terms:

First term:  

Second term:  

Third term:  

Notice that all of the terms are like terms (contain the same radical part and variable part) so they can be combined:

the largest number of the four options is 1.8 x 10-2

you have it in scientific notation.

1.80 x 10-6   = 0.00000180

1.80 x 10-4   = 0.000180 (bigger, or "less small", than the former one)

so

1.8 x 10-2       = 0.0180. as you see. the "less small", or the biggest one of them all.

as you have negative exponent, it means you are dividing 1.8 by 100 (i.e. moving the dot towards left, two times).

if you had positive exponent for the scientific notation, power of tenths, you would be multiplying times 100 (moving the dot towards right) as below:

1.8 x (10)2 = 180

so. if you have negative exponent in scientific notation, move the dot toward left. if it is positive, toward right as many times the exponent tells you.