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# How to solve this equation?

y=3x^2+72

y=24-30x

### 4 Answers

- Anonymous9 years agoFavorite 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!