Question 981387
Same as what you may already know.


{{{3(x+5y)^2-3*2*c(x+5y)+5c(x+5y)-10c^2}}}


{{{3(x^2+10xy+25y^2)-6c(x+5y)+5c(x+5y)-10c^2}}}



{{{3x^2+30xy+75y^2-6cx-30cy+5cx+25cy-10c^2}}}


{{{highlight(3x^2+30xy+75y^2-cx-5cy-10c^2)}}}
Terms may be arranged differently.