Daniel Poon's answer to Isaac's Secondary 1 Maths Singapore question.
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Notice that the height of triangle ADF is equal to AE, which is the side of the square. So AE = 3x + 2. Use the formula for the area of a triangle, but remember that the base of the triangle is DF and not just DE!
Once you have found the area of ADF in terms of x, solve for x. Remember that the expansion of (ax + b)^2 is (a^2)(x^2) + 2(ax)(b) + b^2. Use this identity to find the area of the square in terms of x, then substitute the value of x to obtain the numerical answer.
Once you have found the area of ADF in terms of x, solve for x. Remember that the expansion of (ax + b)^2 is (a^2)(x^2) + 2(ax)(b) + b^2. Use this identity to find the area of the square in terms of x, then substitute the value of x to obtain the numerical answer.
Date Posted:
2 years ago
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