Question

resolva a equação de 2 grau : x2-4x=4

Answer 1

$x^2-4x=4\to\\\\ x^{2} -4x-4=0\\\\ a=1;b=-4;c=-4\\\\\\ \Delta=b^2-4ac\to \Delta=(-4)^2-4*1*(-4)\to \Delta=16+16\to \Delta=32\\\\ x' \neq x''\\\\\\ x= \frac{-b\pm \sqrt{\Delta} }{2a} \to x= \frac{-(-4)\pm \sqrt{32} }{2*1} \to x= \frac{4\pm 4\sqrt{2} }{2} \to \\\\ x'= \frac{4+ 4\sqrt{2} }{2} \to x'= 2+2\sqrt{2} \\\\ x''= \frac{4- 4\sqrt{2} }{2} \to x''= 2- 2\sqrt{2} \\\\\\ S=\{2-2\sqrt{2};2+2\sqrt{2} \}$