Question

(x-3y)2+9y(x-y)
При x=-3
y= 3 1/9
СРОЧНО ДАЮ 50 Баллов

Answer 1

$\displaystyle\bf\\(x-3y)^{2} +9y(x-y)=x^{2} -6xy+9y^{2} +9xy-9y^{2} =\\\\\\=x^{2} +\underbrace{(9xy-6xy)}_{3xy}+\underbrace{(9y^{2} -9y^{2})} _{0}=x^{2} +3xy\\\\x=-3 \ \ ; \ \ y=3\frac{1}{9} \\\\\\x^{2} +3xy=(-3)^{2}+3\cdot(-3)\cdot \frac{28}{9} =9-28=-19\\\\\\Otvet:-19$