Question

Resolva a equação 2x ao quadrado+21x+40=0

Answer 1

$2 x^{2} +21x+40=0\\\\ a=2;b=21;c=40\\\\\\ \Delta=b^2-4ac\to \Delta=21^2-4*2*40\to \Delta=441-320\to \Delta=121\\\\ \Delta\ \textgreater \ 0\to x' \neq x''\\\\\\ x= \frac{-b\pm \sqrt{\Delta} }{2a} \to x= \frac{-21\pm \sqrt{121} }{2*2} \to x= \frac{-21\pm 11}{4} \to \\\\\\ x'= \frac{-21+ 11}{4} \to x'= \frac{-10}{4} \to x= -\frac{5}{2} \\\\\\ x''= \frac{-21- 11}{4} \to x''= \frac{-32}{4} \to x''=-8\\\\\\\\ S= \left \{ -8;-\frac{5}{2} \left \}$