What is the axis of symmetry and vertex for the graph #y= -3x^2 + 4 #?

1 Answer
Apr 28, 2016

The y-axis is the axis of symmetry and vertex is (0;4)


You should notice that:
1.) It is a quadratic (#x^2#) and therefore the graph is a parabola.
2.) The value of #a# is -3, therefore the parabola is 'upside down' and has a maximum turning point.
3.) There is no #x# term, therefore the parabola has not moved to the left or right, it is symmetrical about the y-axis which is then the axis of symmetry. (the line #x# = 0)
4.) The constant term, #c#, has the value 4, which is the y-intercept. The parabola has been moved 4 units upwards.
All points on the y-axis have the form (0;y)

Hence the vertex, or turning point, is the point (0,4).