angrytan's answer to Hii's Secondary 2 Maths Singapore question.
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Area of rectangle = (2x+5)(2x-1)
= 4x^2 + 10x - 2x - 5
= 4x^2 + 8x - 5
Area of rectangle = 3 times of square
4x^2 + 8x - 5 = 3(x + 1)^2
4x^2 + 8x - 5 = 3x^2 + 6x + 3
x^2 + 2x - 8 = 0 (proven)
x^2 + 2x - 8 = 0
(x+4)(x - 2) = 0
x = -4 or x = 2
= 4x^2 + 10x - 2x - 5
= 4x^2 + 8x - 5
Area of rectangle = 3 times of square
4x^2 + 8x - 5 = 3(x + 1)^2
4x^2 + 8x - 5 = 3x^2 + 6x + 3
x^2 + 2x - 8 = 0 (proven)
x^2 + 2x - 8 = 0
(x+4)(x - 2) = 0
x = -4 or x = 2
Date Posted:
4 years ago
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