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Secondary 1 | Maths
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Pls help...
Date Posted: 4 years ago
Views: 246
-3x² + 2x + 6 = 0
3x² - 2x - 6 = 0 (either multiply by -1 on both sides of equation or bring over each term to the right)
x² - ⅔x - 2 = 0 (divide by 3)
x² - 2(⅓)x + (⅓)² - (⅓)² - 2 = 0
The first 3 terms are now in the form
a² - 2(a)(b) + b² and can be rewritten as (a - b)²
(x - ⅓)² - 1/9 - 2 = 0
(x - ⅓)² = 2 + 1/9 = 19/9
x - ⅓ = √(19/9) or x - ⅓ = -√(19/9)
x = ⅓ + √(19/9) + ⅓ or x = ⅓ - √(19/9)
x ≈ 1.79 or x ≈ -1.12
(2d.p)
3x² - 2x - 6 = 0 (either multiply by -1 on both sides of equation or bring over each term to the right)
x² - ⅔x - 2 = 0 (divide by 3)
x² - 2(⅓)x + (⅓)² - (⅓)² - 2 = 0
The first 3 terms are now in the form
a² - 2(a)(b) + b² and can be rewritten as (a - b)²
(x - ⅓)² - 1/9 - 2 = 0
(x - ⅓)² = 2 + 1/9 = 19/9
x - ⅓ = √(19/9) or x - ⅓ = -√(19/9)
x = ⅓ + √(19/9) + ⅓ or x = ⅓ - √(19/9)
x ≈ 1.79 or x ≈ -1.12
(2d.p)
See 1 Answer
done
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clear
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Use the general formula. Becareful of the negative values, easily make careless mistake.
Date Posted:
4 years ago
I am surprised that Sec 1 students are taught to use the quadratic formula or completing the square.
It's likely to be either a wrongly labelled question or the student is in an IP school. They tend to teach such concepts very early.
Btw Kamal, it's clear that the question asked for the method of completing the square, so providing the quadratic formula as your suggested answer isn't quite relevant, though good effort
Im sorry J.
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