Cubic Equation where c = 0

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kiwifruit

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Feb 12, 2015
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Hello
I was wondering if someone could help. I am in my forties and my days of calculus at school are long behind me.
For work I am stuck with a Cubic equation like this:

ax^3 + bx^2 + d = 0

or you could write ax^3 + bx^2 + 0x + d = 0

i know that the value of a = 2
b = p + q + r
d = - (p * q * r)

I want to be able to fill in the values for p, q and r, and then figure out the value of x.

If anyone could help, that would be fantastic.
Thanks.
 
kiwifruit said:
Hello
I was wondering if someone could help. I am in my forties and my days of calculus at school are long behind me.
For work I am stuck with a Cubic equation like this:

ax^3 + bx^2 + d = 0

or you could write ax^3 + bx^2 + 0x + d = 0

i know that the value of a = 2
b = p + q + r
d = - (p * q * r)

I want to be able to fill in the values for p, q and r, and then figure out the value of x.

If anyone could help, that would be fantastic.
Thanks.
Click to expand...
Just like a quadratic equation has a formula so does a cubic equation
In that formula plug in 2 for a, (p+q+r) for b, 0 for c and -pqr for d.
This cubic formula is not very friendly and with your values for b and it will be messy but doable.
 
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