Derive the Product Form of the Quadratic f(x) = x² + x - 2

Quadratic Factoring with Finding Factor Pairs

Find the representation of the product of the following function

f(x)=x2+x2 f(x)=x^2+x-2

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Convert trinomial to multiplication
00:03 Identify the trinomial coefficients
00:07 We want to find 2 numbers whose sum equals coefficient B
00:12 and their product equals coefficient C
00:17 These are the matching numbers, let's substitute in multiplication
00:24 And this is the solution to the question

Step-by-step written solution

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1

Understand the problem

Find the representation of the product of the following function

f(x)=x2+x2 f(x)=x^2+x-2

2

Step-by-step solution

To determine the product representation of f(x)=x2+x2 f(x) = x^2 + x - 2 , we can factor the quadratic equation by following these steps:

  • Step 1: Identify the product ac=1×(2)=2 ac = 1 \times (-2) = -2 and sum b=1 b = 1 .
  • Step 2: Find two numbers that multiply to 2-2 and add to 11. These numbers are 22 and 1-1.
  • Step 3: Rewrite the middle term using these numbers: x2+2x1x2 x^2 + 2x - 1x - 2 .
  • Step 4: Factor by grouping:
    - Group x2+2x x^2 + 2x and 1x2-1x - 2 as separate pairs:
    - x(x+2)1(x+2) x(x + 2) - 1(x + 2) .
  • Step 5: Factor out the common terms:
    (x+2)(x1)(x + 2)(x - 1).

Thus, the product representation of the function is (x+2)(x1) (x + 2)(x - 1) .

3

Final Answer

(x+2)(x1) (x+2)(x-1)

Key Points to Remember

Essential concepts to master this topic
  • Product-Sum Method: Find two numbers that multiply to ac ac and add to b b
  • Factor by Grouping: Rewrite x2+x2 x^2 + x - 2 as x2+2xx2 x^2 + 2x - x - 2 then group pairs
  • Verify: Expand (x+2)(x1)=x2+x2 (x+2)(x-1) = x^2 + x - 2 to confirm factoring ✓

Common Mistakes

Avoid these frequent errors
  • Getting the signs wrong in the factored form
    Don't just focus on finding numbers 2 and -1 without checking their placement = wrong signs like (x-2)(x+1)! The numbers 2 and -1 must be positioned so they create the correct middle term when expanded. Always verify by expanding your factored form back to the original.

Practice Quiz

Test your knowledge with interactive questions

Create an algebraic expression based on the following parameters:

\( a=3,b=0,c=-3 \)

FAQ

Everything you need to know about this question

How do I know which two numbers to look for?

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You need two numbers that multiply to give ac (the product of the coefficient of x2 x^2 and the constant term) and add to give b (the coefficient of x). For x2+x2 x^2 + x - 2 , find numbers that multiply to -2 and add to 1.

What if I can't find two numbers that work?

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Double-check your ac and b values first! If you still can't find suitable numbers, the quadratic might not factor nicely with integers, and you may need to use the quadratic formula instead.

Why do we rewrite the middle term?

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Rewriting x x as 2xx 2x - x lets us group terms in pairs that share common factors. This makes it easier to factor out common terms and find the final factored form.

How can I check if my factored answer is correct?

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Simply expand your factored form using FOIL or the distributive property. If you get back the original quadratic, your factoring is correct! For example: (x+2)(x1)=x2x+2x2=x2+x2 (x+2)(x-1) = x^2 - x + 2x - 2 = x^2 + x - 2

What if the coefficient of x² isn't 1?

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The same method works! Just remember that a is the coefficient of x2 x^2 , so ac ac will be different. For 2x2+5x3 2x^2 + 5x - 3 , you'd look for numbers that multiply to 2×(3)=6 2 \times (-3) = -6 and add to 5.

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