Question

5 é raiz de x elevado a 2 - 8x+15=0

Answer 1

$x^{2} - 8x+15=0\\\\ a=1;b=-8;c=15\\\\\\ \Delta=b^2-4ac\to \Delta=(-8)^2-4*1*15\to \Delta=64-60\to \Delta=4\\\\\\ x= \frac{-b+- \sqrt{\Delta} }{2a} \to x= \frac{-(-8)+- \sqrt{4} }{2*1} \to x= \frac{8+-2 }{2} \to \\\\\\ x'= \frac{8+2 }{2} \to x'= \frac{10 }{2} \to x'= 5\\\\\\ x''= \frac{8-2 }{2} \to x''= \frac{6 }{2} \to x''=3\\\\\\ S=(3;5)$


R.: 5 é sim raiz dessa equação, mas 3 também é.