How to solve this equation?

y=3x^2+72

y=24-30x

4 Answers

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  • Anonymous
    9 years ago
    Favorite Answer

    As they both equal y,

    3x^2 + 72 = 24 - 30x

    Rearrange,

    3x^2 + 30x + 48 = 0

    Divide whole eqn by 3

    x^2 + 10x + 16 = 0

    Factorise

    (x + 8)(x + 2) = 0

    x = -8, x = -2

    Now substitute into original eqn 2 to find y,

    y = 24 - 30* -8 and y = 24 - 30 * -2

    y = 24 + 240 and y = 24 + 60

    y = 264 and y = 84

  • 9 years ago

    Both equations tell you what y equals. Since both equal y, set them equal to each other.

    24-30x = 3x^2+72

  • 9 years ago

    That's just a straight line, so quite easy to graph. Just find the x and y intercepts, plot the points and join the line.

    To find the y intercept set x=0

    y=(2/3)(0)+2 --> y=2

    y-int is (0,2)

    To find the x intercept set y=0

    0=(2/3)x+2 --> x=-3

    so x-int is (-3,0)

    Plot those 2 points and connect to draw the graph

  • 9 years ago

    Do I give you the answer or do I give you step by step intrustions on how to solve it?

    Well i'll give you both!

    Solve:

    Since they're both y it's like...

    3x^2+72 = 24-30x

    so to solve it u solve one of them and thats the answer!

    Answer:

    Y=_____

    Source(s): My brain! YOUR WELCOME!
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