all real numbers less than 3

Calcula la lasa de varicion. \( f(x)=2 x^{2}-2 \) en el intervalo \( [1.3] \)

Calcula de dos formas dislintas. \( \begin{array}{ll}\text { a) } 2 \cdot(-4+7) & \text { b) }-5 \cdot(3-6) \\ \text { d } \cdot(-2-1! & \text { d) }-9 \cdot(-8+5)\end{array} \)

Find the number of oranges in a tetrahedron with four layers. The number of oranges in a tetrahedron with \( n \) layers is \( \frac{1}{6} n(n+1)(n+2) \). Check that this expression gives the correct answer with \( n=4 \). c A shopkeeper has 100 oranges. He wants to display them in a tetrahedron. Work out the largest number of layers he can have. dhow how to use the formula to add the first 20 triangular numbers.

3. \( \left\{\begin{array}{l}x-2 y=-5 \\ 2 x-3 y=-4\end{array}\right. \)

5. ข้อใดคือเซตแบบบอกเงื่อนไขของ \( \{\ldots,-2,-1,0,1,2 \), \( \begin{aligned}\text { 3, } \ldots\} & \\ \text { ก. }\left\{x \mid x \in \mathbb{Z}^{+}\right\} & \text {ค. }\{x \mid x \in N\} \\ \text { 6. }\{x \mid x \in \mathbb{Z}\} & \text { ง. }\{x \mid x \in R\}\end{aligned} \)