[tex]5x^2+70x+245=0\\ \\Dividimos\ por\ 5\ a\ toda\ la\ ecuaci\'on\\ \\x^2+14x+49=0\\ \\x=\frac{-14\pm\sqrt{14^2-4\cdot1\cdot49}}{2}=\frac{-14\pm\sqrt{0}}{2}=\frac{-14\pm0}{2}\\ \\x_1=\frac{-14+0}{2}=-7\\ \\x_2=\frac{-14-0}{2}=-7\\ \\x_1=x_2=-7[/tex]
[tex]x^2+14x+49=(x-(-7))(x-(-7))=(x+7)(x+7)=(x+7)^2\\ \\x^2+14x+49=(x+7)^2\\ \\Si\ resolvemos\\ \\(x+7)^2=0==>x+7=0\ ;\ x=-7[/tex]
la solución es x=-7
