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Today’s topic is inequalities, expressions like \(a\geq b\), or \(a>b\). There are certain rules for operating inequalities: one can subtract the same number from both sides of the inequality, namely if \(a\geq b\), then \(a-b \geq 0\). If \(a \geq b\) and \(b\geq c\), then \(a\geq c\). If a number \(c\geq 0\), then from \(a\geq b\) it follows that \(ac \geq bc\). However, in case of multiplication by a negative number \(c\leq 0\), the inequality sign reverses: from \(a\geq b\) it follows that \(ac \leq bc\). One should also remember that the square of any real number is non-negative.

Draw how Robinson Crusoe should put pegs and ropes to tie his goat in order for the goat to graze grass in the shape of a square, or slightly harder in a shape of a given rectangle.

Draw how Robinson Crusoe should put pegs and ropes to tie his goat in order for the goat to graze grass in the shape of a parallelogram.

Draw how Robinson Crusoe should put pegs and ropes to tie his goat in order for the goat to graze grass in the shape of a shape like this

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Draw how Robinson Crusoe should put pegs and ropes to tie his goat in order for the goat to graze grass in the shape of a given triangle.

Draw how Robinson Crusoe should put pegs and ropes to tie his goat in order for the goat to graze grass in the shape of a hexagon

Draw a picture how Robinson used to tie the goat and the wolf in order for the goat to graze the grass in the shape of half a circle.

Draw a picture how Robinson used to tie the goat and the wolf in order for the goat to graze the grass in the shape of a young moon (see the picture below)

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Draw a picture how Robinson used to tie the goat and the wolf in order for the goat to graze the grass in the shape of half a ring.

Each number denotes the area of a rectangle it is written into. What is the area of the last rectangle? (That is, the yellow one)

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