Find the value of P

Algebra Level 3

Given that x 2 + 2 x 3 = 0 x^2 + 2x - 3 = 0 and x 2 + 3 x + p = 0 x^2 + 3x + p = 0 have a common root. Find the value of p p .

Bonus : Form the equation with the other two roots which are not common.

None of the above P = 0 ; x^2 = 0 or x^2 - 7x + 12 = 0 P={0,-4} ; x^2 - x = 0 or x^2 + 7x + 12 = 0 P = -4 ; x^2 - x = 0 or x^2 + 7x - 12 = 0

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1 solution

Christian Daang
Nov 16, 2014

p = {0, -4}

And the equations are: x^2 - x = 0 or x^2 + 7x + 12 = 0

Given:

x^2 + 2x - 3 = 0 = x^2 + 3x + p ----> x = -(3+p)

s0, x^2 + 2x - 3=0 --> (x+3)(x-1) = 0 ---> x = {-3, 1}

then,

x^2 + 2x - 3 = 0 ---> (-3-p)^2+ 2(-3-p) - 3 = 0

= p^2 + 4p = 0 ---> p = {0, -4}

Then,

If p = 0 ,

x^2 + 3x = 0 ---> x(x+3) = 0 ---> x = {0,-3} roots that are not common: x = {0,1} then, the equation is: x^2 - x = 0

If p = -4 ,

x^2 + 3x - 4 = 0 ---> x = {-4, 1} roots that are not common: x = {-4, -3} then, the equation is: x^2 + 7x + 12 = 0

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