Question

2) Qual o valor de x para a equação 5.(2 + 2x + 4) = 100 + 5x ?

Answer 1

$5x(2 + 2x + 4) = 100 + 5x \\10x^2+30x=100+5\\10x^2+30x-5x=100+5x-5x\\10x^2+25x-100=100-100\\10x^2+25x-100=0\\= \frac{-25\pm\sqrt{25^2-4x10(-100)} }{2x10}\\\sqrt{25^2-4x10(-100)}=5\sqrt{185}\\=\frac{-25\pm5\sqrt{185} }{2x10}\\=\frac{-25+5\sqrt{185} }{2x10} = =\frac{-25-5\sqrt{185} }{2x10}\\x=\frac{-25+5\sqrt{185} }{2x10} = \frac{-5+\sqrt{185} }{4}\\x=\frac{-25-5\sqrt{185} }{2x10} = \frac{-5-\sqrt{185} }{4}\\x=\frac{-25-5\sqrt{185} }{2x10} = -\frac{-5+\sqrt{185} }{4}$

$x=\frac{-5+\sqrt{185} }{2x10} = -\frac{-5+\sqrt{185} }{4}$