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check and tell where I went wrong PLEASE

What is the axis of symmetry for y=x^2+7x+10

A x=7

B x=-7/2

C=7/2

D=x=-7

And this is what I got and I do not know where I went wrong but I did:

Factor:

y=x^2+7x+10

= (x+2)(x+5) = 0

x= -2

x = -5

average of the two x-values is -3.5

so the axis of symmetry is the line x= -3.5

2 Answers

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  • 1 decade ago
    Favorite Answer

    yes you're right

  • 1 decade ago

    You can sort of imagine the graph to be like a U-shaped curve, with the the vertical line passing through the lowest point of the curve (ie. the point where the slope of the graph is 0).

    y = x^2 + 7x + 10

    dy/dx = 2x + 7

    When slope = 0, dy/dx = 0.

    2x + 7 = 0

    x = -7/2

    So you're correct. If you haven't learned about differentiation, then your method is correct.

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