$\"\"$

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Observe the square and side is $\"\"$ .

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The total area of the square $\"\"$ .

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The value of $\"\"$ is substitute in the formula $\"\"$ .

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$\"\"$

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Apply formula: $\"\"$ .

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$\"\"$

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$\"\"$ . $\"\"$

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The side of the cutting square is 5 cm.

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The area of the cutting square $\"\"$ .

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The value of $\"\"$ is substitute in the formula $\"\"$ .

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$\"\"$ .

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The area of the shaded region = Total area of the square $\"\"$ cutting square area.

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$\"\"$

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$\"\"$ $\"\"$

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The shaded region area is equal to the area of the rectangle.

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The area of the rectangle is $\"\"$ .

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The factor form of $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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The area of the rectangle is $\"\"$ . $\"\"$

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(a)The area of the shaded region $\"\"$ .

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(b)The dimensions of rectangle $\"\"$ .