Question

Me ajudam pf nessas contas!!

Answer 1

$a)\\\\(y-7)(y+1)=y^{2} +5\\ \\ y^{2} +y-7y-7=y^{2} +5\\ \\ y^{2}-y^{2} +y-7y=5+7\\ \\ -6y=12~.~(-1)\\ \\ 6y=-12\\ \\ y=-\frac{12}{6} \\ \\ y=-2$

$b)\\ \\ x(x+9)=(x+3)(x-3)\\ \\ x^{2} +9x=x^{2} -9\\ \\ x^{2}-x^{2} +9x=-9\\ \\ 9x=-9\\ \\ x=-\frac{9}{9} \\ \\ x=-1$

$c)\\ \\(x+2)(x-2)=(x-3)(x+7)\\ \\ x^{2} -4=x^{2}+7x-3x-21\\ \\x^{2}-x^{2} -7x+3x=-21+4\\ \\ -4x=-17\\ \\ x=\frac{-17}{-4} \\ \\ x=\frac{17}{4}$

$d)\\ \\ (y-1)^{2} =(y+1)^{2} \\ \\ y^{2} -2.y.1+1^{2} =y^{2} +2.y.1+1^{2} \\ \\ y^{2}- y^{2} -2y-2y=1-1\\ \\ -4y=0\\ \\ y=\frac{0}{-4} \\ \\ y=0$