What is the standard form of #y=(2x-3)(x+5) #?

To get the standard form multiply these two terms. To solve you multiply each individual term in the left parenthesis by each individual term in the right parenthesis.

#y = (color(red)(2x) - color(red)(3))(color(blue)(x) + color(blue)(5))# becomes:

#y = (color(red)(2x) xx color(blue)(x)) + (color(red)(2x) xx color(blue)(5)) - (color(red)(3) xx color(blue)(x)) - (color(red)(3) xx color(blue)(5))#

#y = 2x^2 + 10x - 3x - 15#

We can now combine like terms:

#y = 2x^2 + (10 - 3)x - 15#

#y = 2x^2 + 7x - 15#