SOLUTION: Solve for X: X^2 + 3X

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Question 1025135: Solve for X:
X^2 + 3X - 28 = 0

Found 3 solutions by Alan3354, ikleyn, mbessearch:
Answer by Alan3354(69443)   (Show Source):
You can put this solution on YOUR website!
X^2 + 3X - 28 = 0
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find a pair of factors of 28 that differ by 3.

Answer by ikleyn(52788)   (Show Source):
You can put this solution on YOUR website!
.
Solve for X:
X^2 + 3X - 28 = 0
~~~~~~~~~~~~~~~~~~~~~

=

Factor left side polynomial.

You will get an equivalent equation

(x+7)*(x-4) = 0.

The roots are x = -7 and x = 4.

Answer by mbessearch(2)   (Show Source):
You can put this solution on YOUR website!
Polynomial equations, which have two answers.
Equations in this form are likely (especially on a test) created by (x+a)(x+b)=0.
Either x+a=0 or x+b=0
Given the simplicity of this problem what are the factors of 28 that have a difference of 3
28, 1 nope. 14, 2 nope, 7, 4 yes!
We know that one must be negative and one positive. Since the second term in the original question si positive, the answers are a and b are 7 and -4.
Going back to find x, we have x+7=0 and x-4=0. Solving for x we get -7 and 4.
Testing them in the original equation proves they are correct.

SOLUTION: Solve for X: X^2 + 3X - 28 = 0