Question

СРОЧНО!!!!!!!!!!!!!!!!!!!!!!!!!!!

Answer 1

$\displaystyle\bf\\\Big(7x^{2} - y^{2} \Big)+\Big(2x^{2} +5xy-2y^{2} \Big)=7x^{2} - y^{2} +2x^{2} +5xy-2y^{2} =\\\\\\=\Big(\underbrace{7x^{2} +2x^{2}}_{9x^{2} } \Big)-\Big(\underbrace{y^{2} +2y^{2}}_{3y^{2}} \Big) +5xy=9x^{2} -3y^{2} +5xy$