You need to clarify your question. Depending on what you mean, the answer could be:
or many other things.
125x squared
To multiply (5x) by (x^2), you multiply the coefficients and add the exponents of the variables. The coefficient is 5, and the exponent of (x) in (5x) is 1. So, (5x \times x^2 = 5x^{1+2} = 5x^3).
15
(3x2)2 (5x)4 = 9x4625x4 = 5625x8
25
5x cubed
125x squared
It is 5x2 - 20
(5x)2 = 25x2.
5x X x^(2) = 5x^(3) ; Said as 'five 'x' cubed'.
When you subtract 7x^2 from 5x^2, you get -2x^2.
(5x - 2y)(5x + 2y)
5x squared
-1
15
(3x2)2 (5x)4 = 9x4625x4 = 5625x8
5x2 - 20 = 0x2 - 4 = 0x2 = 4x = +2 and -2