Question

determine o valor de X1 X2: x ao quadrado - 7x - 18 = 0

Answer 1

manda a conta certa pra mim poder fazer a conta pq nao entendi nada

Answer 2

\mathrm{Para\:}\quad a=1,\:b=-7,\:c=-18:\quad x_{1,\:2}=\frac{-\left(-7\right)\pm \sqrt{\left(-7\right)^2-4\cdot \:1\left(-18\right)}}{2\cdot \:1}

\frac{-\left(-7\right)+\sqrt{\left(-7\right)^2-4\cdot \:1\cdot \left(-18\right)}}{2\cdot \:1}

=\frac{7+\sqrt{\left(-7\right)^2+4\cdot \:1\cdot \:18}}{2\cdot \:1}

=\frac{7+\sqrt{\left(-7\right)^2+1\cdot \:4\cdot \:18}}{2}

\frac{7+\sqrt{121}}{2}

\sqrt{121}

=\sqrt{11^2}

\frac{7+11}{2}

=\frac{18}{2}=9

\frac{7-11}{2}

=\frac{-4}{2}=-2

x1=9 e x2=-2