# Homework Help: Quadratic and cubic equation -show that -(common roots)

1. Aug 20, 2011

### Sumedh

1. The problem statement, all variables and given/known data

If the equations ax2+bx+c=0 and x3+3x2+3x+2=0 have two common solutions then show a=b=c.

2. Relevant equations

3. The attempt at a solution

first equation will be the factor of second.
taking out common from first equation.

how to show a=b=c??

2. Aug 20, 2011

### SammyS

Staff Emeritus
Find a real root of the cubic equation. Write the cubic polynomial as the product of a quadratic factor and a linear factor.

3. Aug 20, 2011

### PeterO

factorise the cubic.

4. Aug 20, 2011

### uart

The easiest way to approach this is to divide (x^3 + 3x^2+ 3x + 2) by (x^2 + x +1) to prove that it's a factor. You don't actually need to factorize, just verify that the factor.

5. Aug 20, 2011

### Sumedh

can we solve by the following formulas

α+ß =-b/a

αß= c/a

for cubic equations
(Γ=gamma)

α+ß+Γ=-b/a

(αß)+(ßΓ)+(αΓ)=c/a

αßΓ=-d/a

i am trying to solve by this method but i hung up! in between?

6. Aug 20, 2011

### Sumedh

thank you very much i got it