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
00:10 Let's solve the equation step by step.
00:15 First, arrange the equation so the right side equals zero.
00:31 Next, collect like terms together.
00:54 Now, divide everything by seven to simplify.
01:05 Calculate each fraction carefully.
01:11 We're going to factor using a trinomial.
01:16 Find two numbers that add up to B.
01:20 And their product should equal C.
01:27 These are the right numbers to use.
01:32 Place these numbers inside brackets.
01:38 Find what makes each bracket equal zero.
01:46 This gives us one solution.
01:50 Now, let's find the second solution.
01:56 Here's the second solution.
02:00 And that's how we solve the equation!

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

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

What is the value of X?

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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