Question

срочно!!алгебра,даю 60 балок

Answer 1

$\displaystyle\bf\\1)\\\\3ab-4ab+7b^{2} =7b^{2} -ab\\\\\\2)\\\\5m^{2} +4m-8m-2m^{2} -3m^{2} =\underbrace{\Big(5m^{2} -2m^{2} -3m^{2} \Big)}_{0}+\Big(4m-8m\Big)=\\\\=-4m\\\\\\3)\\\\7x^{3} \cdot(-x)y+2x^{2} \cdot 3x^{5} =-7x^{4}y +6x^{7} =6x^{7} -7x^{4} y$