Question

алгебра 7 класс,помогите!!

Answer 1

$\displaystyle\bf\\1)\\\\64x^{2} -16y^{2} =16\cdot(4x^{2} -y^{2} )=16\cdot\Big[(2x)^{2} -y^{2}\Big ]=16(2x-y)(2x+y)\\\\\\2)\\\\-x^{2} -18xy-81y^{2} =-(x^{2} +18xy+81y^{2} )=-\Big[x^{2} +2\cdot x\cdot 9y+(9y)^{2} \Big]=\\\\=-(x+9y)^{2} \\\\\\3)\\\\a-b+a^{2} -b^{2} =(a-b)+(a^{2} -b)^{2} =(a-b)+(a-b)(a+b)=\\\\=(a-b)(1+a+b)$