Solve Quadratic Equation: Finding X in 2x²+4x-6=0

Quadratic Equations with Factoring Method

2x2+4x6=0 2x^2+4x-6=0

Solve the following quadratic equation:

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find X
00:03 Divide to reduce the trinomial coefficients
00:20 Pay attention to the trinomial coefficients
00:26 We want to find 2 numbers
00:36 whose sum equals B and their product equals C
00:40 These are the matching numbers
00:51 Therefore these are the numbers we'll put in parentheses
00:55 Find the solutions that zero each factor
00:59 Isolate X, this is one solution
01:06 Isolate X, this is the second solution
01:16 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

2x2+4x6=0 2x^2+4x-6=0

Solve the following quadratic equation:

2

Step-by-step solution

Let's solve the given equation:

2x2+4x6=0 2x^2+4x-6=0

Let's first simplify the equation, noting that all coefficients as well as the free term are multiples of the number 2, hence we'll divide both sides of the equation by 2:

2x2+4x6=0/:2x2+2x3=0 2x^2+4x-6=0 \hspace{6pt}\text{/}:2 \\ x^2+2x-3=0\\ Note that the coefficient of the squared term is 1, therefore we can (try to) factor the expression on the left side using quick trinomial factoring:

We'll look for a pair of numbers whose product equals the free term in the expression, and whose sum equals the coefficient of the first-degree term, meaning two numbers m,n m,\hspace{2pt}n that satisfy:

mn=3m+n=2 m\cdot n=-3\\ m+n=2\\ From the first requirement mentioned, that is - from the multiplication, we notice that the product of the numbers we're looking for needs to yield a negative result, therefore we can conclude that the two numbers have different signs, according to multiplication rules. The possible factors of 3 are 3 and 1. Fulfilling the second requirement mentioned, along with the fact that the signs of the numbers we're looking for are equal to each other will lead to the conclusion that the only possibility for the two numbers we're looking for is:

{m=3n=1 \begin{cases}m=3 \\ n=-1\end{cases}

Therefore we'll factor the expression on the left side of the equation to:

x2+2x3=0(x+3)(x1)=0 x^2+2x-3=0\\ \downarrow\\ (x+3)(x-1)=0

From here we'll remember that the result of multiplication between expressions will yield 0 only if at least one of the multiplying expressions equals zero,

Therefore we'll obtain two simple equations and solve them by isolating the unknown on one side:

x+3=0x=3 x+3=0\\ \boxed{x=-3}

or:

x1=0x=1 x-1=0\\ \boxed{x=1}

Let's summarize the solution of the equation:

2x2+4x6=0x2+2x3=0(x+3)(x1)=0x+3=0x=3x1=0x=1x=3,1 2x^2+4x-6=0 \\ x^2+2x-3=0 \\ \downarrow\\ (x+3)(x-1)=0 \\ \downarrow\\ x+3=0\rightarrow\boxed{x=-3}\\ x-1=0\rightarrow\boxed{x=1}\\ \downarrow\\ \boxed{x=-3,1}

Therefore the correct answer is answer B.

3

Final Answer

x1=1,x2=3 x_1=1,x_2=-3

Key Points to Remember

Essential concepts to master this topic
  • Simplification: Divide all terms by GCF to reduce coefficients first
  • Factoring: Find two numbers that multiply to 3 -3 and add to 2 2 : 3 3 and 1 -1
  • Verification: Check both solutions: 2(1)2+4(1)6=0 2(1)^2+4(1)-6=0 and 2(3)2+4(3)6=0 2(-3)^2+4(-3)-6=0

Common Mistakes

Avoid these frequent errors
  • Forgetting to simplify coefficients before factoring
    Don't try to factor 2x2+4x6=0 2x^2+4x-6=0 directly = messy factorization with large numbers! This makes finding factor pairs much harder and leads to calculation errors. Always divide by the GCF first to get simpler coefficients like x2+2x3=0 x^2+2x-3=0 .

Practice Quiz

Test your knowledge with interactive questions

\( x^2+6x+9=0 \)

What is the value of X?

FAQ

Everything you need to know about this question

Why do I need to divide by 2 first?

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Dividing by the greatest common factor (GCF) simplifies your work! Instead of finding factors of 6 -6 that work with coefficient 4 4 , you only need factors of 3 -3 that work with coefficient 2 2 .

How do I find the right factor pair?

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Look for two numbers that multiply to give the constant term and add to give the middle coefficient. For x2+2x3 x^2+2x-3 , you need: multiply to 3 -3 , add to +2 +2 . That's 3 3 and 1 -1 !

What if the quadratic doesn't factor nicely?

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Not all quadratics factor with nice integers! If you can't find integer factor pairs, you might need to use the quadratic formula instead: x=b±b24ac2a x = \frac{-b \pm \sqrt{b^2-4ac}}{2a}

Why do I get two different answers?

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Quadratic equations typically have two solutions because a parabola can cross the x-axis at two points. When (x+3)(x1)=0 (x+3)(x-1)=0 , either factor can equal zero, giving you x=3 x=-3 or x=1 x=1 .

Do I always write the smaller solution first?

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Convention varies, but many textbooks list solutions from smallest to largest. The important thing is to find both correct solutions - the order doesn't affect your grade!

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