Odpowiedzi

2010-02-02T19:48:34+01:00
(3x+y)²-(y+4)(y-4)-x(x+5y)=9x²+y²-y²-4y+4y+16-x²-5xy=
=8x²+16-5xy=8*(5/2)²+16-5*5/2*(-1⅕)=8*25/4+16-25/2*(-1⅕)=
=50+16+25/2*6/5=50+16+15=65+16=81