The farmer needs to grow 81 square kilometers of corn to make a profit. Since his field must be a square to hold that area, the length of each side of the square field must be the square root of 81, which is 9 kilometers. Therefore, the sides of the farmer's corn field are each 9 kilometers long.

1. Warm up 3 4 5 A farmer knows he needs to grow an area of 81 km2 of corn to make a profit. His field is a square. How long are the sides of his corn field?

2. Warm up correction

3. Homework correction

4. So, what is a rational number again?

5. Are the following numbers rational?Why? -7/10 -12 2.34 0.666.... 0.172458917245891724589....

6. So, are all numbers rational then?

8. Square root of a number Square of a number a: The number times itself : axa = a2 Examples:

9. Square root of a positive number b: ·a number c so that c2= b ·Each positive number has a positive and negative square root ·The notation for the positive square root of a number is √ Example:

10. Perfect squares

12. Applications with partner