What is the x-coordinate of the vertex of the parabola whose equation is #y=3x^2+9x#? Algebra 1 Answer Tony B Apr 11, 2016 #x_("vertex")=-3/2# Explanation: write as:#" " y=3(x^2+3x)# Consider the 3 from #3x# and apply #x_("vertex")=(-1/2)xx(+3) = -3/2# Answer link Related questions How do I determine the molecular shape of a molecule? What is the lewis structure for co2? What is the lewis structure for hcn? How is vsepr used to classify molecules? What are the units used for the ideal gas law? How does Charle's law relate to breathing? What is the ideal gas law constant? How do you calculate the ideal gas law constant? How do you find density in the ideal gas law? Does ideal gas law apply to liquids? Impact of this question 4360 views around the world You can reuse this answer Creative Commons License