Question

Os zeros da função f da pela lei f(x)=x(x +1)-12 são: *


a) S={(+3,+4)}

b) S={(-3,+4)}

c) S={ }

d) S={(+3,-4)}

S={(-3,-4)}

Answer 1

$f(x)=x(x+1)-12\\ f(x)=x^2+x-12\\ \\ x^2+x-12=0 \\ \\ a=1\\ b=1\\ c=-12\\ \\ \Delta=b^2-4ac\\ \Delta=1^2-4(1)(-12)\\ \Delta=1+48\\ \Delta=49\\ \\ {-b\pm\sqrt{\Delta} \over2a}={-1\pm\sqrt{49} \over2.(1)}={-1\pm7\over2}\\ \\ x'={-1-7\over2}={-8\over2}=-4\\ \\ x"={-1+7\over2}={6\over2}=3\\ \\ S=\{-4,3\}~~~letra D$