help? pleaseeee:)
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That graph is a parabola like this: http://en.wikipedia.org/wiki/File:Parabo… , so its line of symmetry is a vertical line. To find the line of symmetry, you need to find the x position of the lowest point on the parabola, and you do this by completing the square:
y = 3x^2 - 5x - 10
= 3(x^2 - (5/3)x - 10/3)
... once it's in this form (x^2 term is 1) you simply halve the x term to complete the square:
= 3( (x - 5/6)^2 + something))
("something" is a constant term, it doesn't matter what it is for our purposes)
So this is enough to tell us that the lowest point is at (x - 5/6)=0, i.e. x = 5/6
So the line of symmetry is the vertical line x = 5/6
y = 3x^2 - 5x - 10
= 3(x^2 - (5/3)x - 10/3)
... once it's in this form (x^2 term is 1) you simply halve the x term to complete the square:
= 3( (x - 5/6)^2 + something))
("something" is a constant term, it doesn't matter what it is for our purposes)
So this is enough to tell us that the lowest point is at (x - 5/6)=0, i.e. x = 5/6
So the line of symmetry is the vertical line x = 5/6