please help with this problem
3x^3+4x^2=27x+36

Question

please help with this problem
3x^3+4x^2=27x+36

misty1212 · Answer

HI!!

misty1212 · Answer

you have a cubic equation to solve?

anonymous · Answer

yes can you please explain all the steps for me

misty1212 · Answer

there is a formula for solving cubes, but it is almost incomprehensible 
start with $$3x^3+4x^2-27x-36=0$$ and then make an educated guess , which is really all you ca ndo

misty1212 · Answer

i guess 3, since 1 and -1 do not work 
shall we try it?

anonymous · Answer

ok

misty1212 · Answer

i;ll be damned, it works!

misty1212 · Answer

got it in the first try 
so this is 
$$(x-3)(\text{ some quadratic})$$which you can find using synthetic division or long division (ugh) or thinking (or cheating)

misty1212 · Answer

i can't write synthetic division here, but i can cheat or think
you pick

anonymous · Answer

idk

misty1212 · Answer

http://www.wolframalpha.com/input/?i=3x%5E3%2B4x%5E2-27x-36%3D0

anonymous · Answer

tnx

johnn. · Answer

Let's solve your equation step-by-step.
3x3+4x2=27x+36
Step 1: Subtract 27x+36 from both sides.
3x3+4x2−(27x+36)=27x+36−(27x+36)
3x3+4x2−27x−36=0
Step 2: Factor left side of equation.
(x+3)(x−3)(3x+4)=0
Step 3: Set factors equal to 0.
x+3=0 or x−3=0 or 3x+4=0
x=−3 or x=3 or x=−43
Answer:
x=−3 or x=3 or x=−43