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How do use use factoring to solve quadratic equations?

What property do you need to use? Can you demonstrate an example of utilizing factoring to solve equations?
Don't forget to include a quadratic equation

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Efe M. | Licensed Energetic, Creative, and Motivational Math TeacherLicensed Energetic, Creative, and Motiva...
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Hi Harry,
 
ax2 + bx + c = 0 is a quadratic equation where a, b and c are all numbers.
 
When factoring a quadratic equation you want to find two numbers (z,y) that satisfy the following if a = 1:
  1. (z)(y) = c
  2. z + y = b 
ax2 + bx + c = 0 can then be written as (x + z)(x + y) = 0. Now we can solve for x since 
x + z = 0 or
x + y = 0
 
Example:
Solve x+ 6x + 8 = 0. 
(2)(4) = 8 and 2+4 = 6. Therefore the factored form is (x + 2)(x + 4) = 0. 
=> x + 2 = 0 => x = -2 OR
x + 4 = 0 => x = -4.
 
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If a is not equal to 1 then you want to find four numbers (e,d,z and y) that satisfy the following:
  1. (e)(d) = a
  2. (z)(y) = c
  3. (e)(y) + (d)(z) = b
Therefore ax2 + x + c = 0 where a is not equal to 1 then it can also be written as (ex + z)(dx + y) = 0.
ex + z = 0 => ex = -z and x = -z/e OR
dx + y = 0 => 
Example:
Solve 6x2 + 11x + 3 = 0
(2)(3) = 6, (3)(1) = 3 and (2)(1) + (3)(3) = 11, therefore (2x + 3)(3x +1) = 0
2x + 3 = 0 => x = -3/2 OR
(3x + 1) = 0 => x = -1/3
 
Hope this helps!
Parviz F. | Mathematics professor at Community CollegesMathematics professor at Community Colle...
4.8 4.8 (4 lesson ratings) (4)
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( X + a) ( X + b) = X2 + ( a +b) X + ab (1) ( X + a) 2 = X2 + 2aX +a2 (2)
 
( X +a ) ( X -a )= X2 -a2  (3)

The 3 above identities are key to factoring quadratic, and finding the roots
 
In general every quadratic, trinomial  aX2  + bX + c is  generated  by multiplication of 2 binomial (linear) expression in the form of 3 identity given above, and subsequently any given Ttrinomial ( quadratic), can
 be factored to binomial factors i.e.( X + a) ( X + b) = X2 + ( a +b) X + ab, that is used in evaluation of roots of the quadratic.
,  .  
 In other words identities (1), (2) , ( 3) can work both ways.
given a quadratic like : X2 + 7X + 10

here we see that ( a + b) = 7 ab =10
a = 2 b =5 is the answer, therefore X2 + 7X + 10 = ( X +2) ( X + 5 )
equation (2) is a special case of (1) where a=b , a+b = 2a , ab=a2
equation (3) is a special case of ( 1) where b = -a, a + ( -a) = 0 , ab = a2

These 3 identities are used in factoring a quadratic.

Equation (1) is factorable if there exists 2 whole number whose sum is ( a+ b), and product =ab.

If the answer of the system of equation is not a whole number, then have to do factoring by competing the square, and come up with a factors of irrational and complex numbers, yielding to Irrational and complex roots .