Solve 3x² + 44x - 50 = -1 - 4x² + 2x: Division-Free Method

Quadratic Equations with Factoring Method

Solve the following exercise without the division operation:

3x2+44x50=14x2+2x 3x^2+44x-50=-1-4x^2+2x

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve
00:05 Arrange the equation so that the right side equals 0
00:21 Collect like terms
00:44 Divide by 7 to reduce
00:55 Calculate each fraction
01:01 Use trinomial to factor, identify the coefficients
01:06 We want to find two numbers whose sum equals B
01:10 and their product equals C
01:17 These are the appropriate numbers
01:22 Put them in brackets
01:28 Find the solutions that make the brackets equal to zero
01:36 This is one solution
01:40 Now let's find the second solution
01:46 And this is the second solution
01:50 And this is the answer to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Solve the following exercise without the division operation:

3x2+44x50=14x2+2x 3x^2+44x-50=-1-4x^2+2x

2

Step-by-step solution

Let's solve the given equation:

3x2+44x50=14x2+2x 3x^2+44x-50=-1-4x^2+2x

First, let's organize the equation by moving terms and combining like terms:

3x2+44x50=14x2+2x3x2+44x50+1+4x22x=07x2+42x49=0 3x^2+44x-50=-1-4x^2+2x \\ 3x^2+44x-50+1+4x^2-2x=0 \\ 7x^2+42x-49=0

Now, instead of dividing both sides of the equation by the common factor of all terms in the equation (which is 7), we'll choose to factor it out of the parentheses:

7x2+42x49=07(x2+6x7)=0 7x^2+42x-49=0 \\ 7(x^2+6x-7)=0

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

However, the first factor in the expression we got is the number 7, which is obviously different from zero, therefore:

x2+6x7=0 x^2+6x-7 =0

Now we notice that in the resulting equation the coefficient of the squared term is 1, therefore, we can (try to) factor the expression on the left side using quick trinomial factoring:

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

mn=7m+n=6 m\cdot n=-7\\ m+n=6\\ From the first requirement mentioned, that is - from the multiplication, we notice that the product of the numbers we're looking for needs to be negative, therefore we can conclude that the two numbers have different signs, according to multiplication rules, and now we'll remember that the possible factors of 7 are 7 and 1, fulfilling the second requirement mentioned, along with the fact that the numbers we're looking for have different signs will lead to the conclusion that the only possibility for the two numbers we're looking for is:

{m=7n=1 \begin{cases} m=7\\ n=-1 \end{cases}

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

x2+6x7=0(x+7)(x1)=0 x^2+6x-7 =0 \\ \downarrow\\ (x+7)(x-1)=0

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

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

x+7=0x=7 x+7=0\\ \boxed{x=-7}

or:

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

Let's summarize the solution of the equation:

3x2+44x50=14x2+2x7x2+42x49=07(x2+6x7)=0x2+6x7=0(x+7)(x1)=0x+7=0x=7x1=0x=1x=7,1 3x^2+44x-50=-1-4x^2+2x \\ 7x^2+42x-49=0 \\ \downarrow\\ 7(x^2+6x-7)=0 \\ \downarrow\\ x^2+6x-7=0\\ \downarrow\\ (x+7)(x-1)=0 \\ \downarrow\\ x+7=0\rightarrow\boxed{x=-7}\\ x-1=0\rightarrow\boxed{x=1}\\ \downarrow\\ \boxed{x=-7,1}

Therefore the correct answer is answer D.

3

Final Answer

7- , 1

Key Points to Remember

Essential concepts to master this topic
  • Rearrangement: Move all terms to one side to get standard form
  • Factoring: Factor out common terms first: 7x2+42x49=7(x2+6x7) 7x^2+42x-49 = 7(x^2+6x-7)
  • Verification: Check both solutions: x=-7 and x=1 in original equation ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting to move all terms to one side
    Don't try to factor while terms are on both sides = impossible to solve! This prevents you from seeing the standard quadratic form. Always rearrange to get everything equal to zero first.

Practice Quiz

Test your knowledge with interactive questions

\( x^2-3x-18=0 \)

FAQ

Everything you need to know about this question

Why can't I just divide both sides by 7 instead of factoring?

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The problem specifically asks for a division-free method! Factoring out the common factor achieves the same result without using division, showing 7(x2+6x7)=0 7(x^2+6x-7)=0 .

How do I know which two numbers multiply to -7 and add to 6?

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Look for factor pairs of 7: only 1 and 7 work. Since the product is negative (-7), the signs must be different. Try +7 and -1: 7×(-1)=-7 and 7+(-1)=6

Why does 7(x²+6x-7)=0 mean x²+6x-7=0?

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When a product equals zero, at least one factor must be zero. Since 7≠0, the other factor (x2+6x7) (x^2+6x-7) must equal zero!

Do I need to check both solutions in the original equation?

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Yes, always! Substitute both x=-7 and x=1 back into 3x2+44x50=14x2+2x 3x^2+44x-50=-1-4x^2+2x to verify they make both sides equal.

What if the quadratic doesn't factor nicely?

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If you can't find integer factors, you might need the quadratic formula instead. But this problem was designed to factor nicely: (x+7)(x1)=0 (x+7)(x-1)=0 .

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