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Here are the solutions to the quadratic equations by factorization:
1. \( x = 10 \) or \( x = 2 \)
2. \( x = -2 \) or \( x = -8 \)
3. \( x = 5 \) or \( x = 8 \)
4. \( x = 7 \) or \( x = -7 \)
5. \( x = \frac{1}{2} \) or \( x = -\frac{3}{2} \)
6. \( x = 1 \) or \( x = 8 \)
7. \( x = -2 \) or \( x = 1 \)
8. \( x = -1 \) or \( x = -5 \)
Solución
Below are step‐by‐step solutions for each of the quadratic equations using factorisation.
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1. Solve (x – 8)(x – 4) = 12
• Expand the left side:
(x – 8)(x – 4) = x² – 4x – 8x + 32 = x² – 12x + 32
• Set the equation to zero by subtracting 12 from both sides:
x² – 12x + 32 – 12 = 0 ⟹ x² – 12x + 20 = 0
• Factor the quadratic. We look for two numbers that multiply to 20 and add to –12. These are –10 and –2:
x² – 12x + 20 = (x – 10)(x – 2)
• Set each factor equal to zero:
x – 10 = 0 ⟹ x = 10
x – 2 = 0 ⟹ x = 2
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2. Solve (x + 4)(x + 6) = 8
• Expand:
(x + 4)(x + 6) = x² + 6x + 4x + 24 = x² + 10x + 24
• Subtract 8 from both sides:
x² + 10x + 24 – 8 = 0 ⟹ x² + 10x + 16 = 0
• Factor the quadratic. Find two numbers that multiply to 16 and add to 10. They are 2 and 8:
x² + 10x + 16 = (x + 2)(x + 8)
• Set each factor to zero:
x + 2 = 0 ⟹ x = –2
x + 8 = 0 ⟹ x = –8
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3. Solve x² – 13x + 40 = 0
• Factor by looking for two numbers that multiply to 40 and add to 13. These are 5 and 8:
x² – 13x + 40 = (x – 5)(x – 8)
• Set each factor equal to zero:
x – 5 = 0 ⟹ x = 5
x – 8 = 0 ⟹ x = 8
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4. Solve x² – 49 = 0
• Recognize this as a difference of two squares:
x² – 49 = (x – 7)(x + 7)
• Set each factor to zero:
x – 7 = 0 ⟹ x = 7
x + 7 = 0 ⟹ x = –7
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5. Solve 4x² + 4x – 3 = 0
• Factor the quadratic. We look for factors in the form (ax + b)(cx + d) such that:
(2x – 1)(2x + 3) expands as:
2x · 2x = 4x²
2x · 3 + (–1) · 2x = 6x – 2x = 4x
(–1)(3) = –3
Thus, 4x² + 4x – 3 = (2x – 1)(2x + 3)
• Set each factor to zero:
2x – 1 = 0 ⟹ 2x = 1 ⟹ x = ½
2x + 3 = 0 ⟹ 2x = –3 ⟹ x = –3/2
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6. Solve 2x(x – 3) + 10 = (x + 1)(x + 2)
• Expand both sides:
Left: 2x(x – 3) + 10 = 2x² – 6x + 10
Right: (x + 1)(x + 2) = x² + 3x + 2
• Bring all terms to one side:
2x² – 6x + 10 – (x² + 3x + 2) = 0
x² – 9x + 8 = 0
• Factor the quadratic. We need two numbers that multiply to 8 and add to –9. They are –1 and –8:
x² – 9x + 8 = (x – 1)(x – 8)
• Set each factor equal to zero:
x – 1 = 0 ⟹ x = 1
x – 8 = 0 ⟹ x = 8
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7. Solve x(x + 1) = 2
• Expand:
x² + x = 2
• Rearrange to bring everything to one side:
x² + x – 2 = 0
• Factor the quadratic. Find two numbers that multiply to –2 and add to 1. They are 2 and –1:
x² + x – 2 = (x + 2)(x – 1)
• Set each factor to zero:
x + 2 = 0 ⟹ x = –2
x – 1 = 0 ⟹ x = 1
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8. Solve (x + 1)(x + 2) + (x + 3)(x + 1) = x(x + 1)
• Notice that (x + 1) is common in the left-hand terms. Factor it out:
(x + 1)[(x + 2) + (x + 3)] = (x + 1)(2x + 5)
• The equation becomes:
(x + 1)(2x + 5) = x(x + 1)
• Subtract x(x + 1) from both sides:
(x + 1)(2x + 5 – x) = 0
(x + 1)(x + 5) = 0
• Set each factor equal to zero:
x + 1 = 0 ⟹ x = –1
x + 5 = 0 ⟹ x = –5
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Summary of Answers:
1. (x – 8)(x – 4) = 12 ⟹ x = 10 or x = 2
2. (x + 4)(x + 6) = 8 ⟹ x = –2 or x = –8
3. x² – 13x + 40 = 0 ⟹ x = 5 or x = 8
4. x² – 49 = 0 ⟹ x = 7 or x = –7
5. 4x² + 4x – 3 = 0 ⟹ x = ½ or x = –3/2
6. 2x(x – 3) + 10 = (x + 1)(x + 2) ⟹ x = 1 or x = 8
7. x(x + 1) = 2 ⟹ x = –2 or x = 1
8. (x + 1)(x + 2) + (x + 3)(x + 1) = x(x + 1) ⟹ x = –1 or x = –5
These are the solutions to the given quadratic equations by factorisation.
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