Export restrictions on cereals like maize anc rice are sometimes imposed in West Africa. What is one primary reason for these restrictions? a. To discourage small-scale farming bavor of industrial agriculture To promote regional trade agreements like ELTS

20. If the expression \( \frac{2 i^{2}-3 i}{1-2 i} \) is written in the form \( a+b i \) where a and \( b \) are real numbers and \( i=\sqrt{-1} \), what is the value of a?

12. Find a standard basis vector for \( R^{3} \) that can be added to the set \( \left\{\mathbf{v}_{1}, \mathbf{v}_{2}\right\} \) to produce a basis for \( R^{3} \). (a) \( \mathbf{v}_{1}=(-1,2,3), \mathbf{v}_{2}=(1,-2,-2) \) (b) \( \mathbf{v}_{1}=(1,-1,0), \mathbf{v}_{2}=(3,1,-2) \)

(b) Show that the relation R on the set \( \mathrm{A}=\{1 \), \( 2,3,4,5\} \) given by \( \mathrm{R}=\{(\mathrm{a}, \mathrm{b}):|\mathrm{a}-\mathrm{b}| \) is even \( \} \) is an equivalence relation.

4. ¿Cuál de estas igualdades es correcta? (A) \( \log _{3} 8=2 \) (B) \( \log _{3} 2=8 \) (C) \( \log _{2} 8=3 \) (D) \( \log _{2} 3=8 \) (D)

5. A psychologist is interested in exploring the effect oftutorial support on student academic performance and assign students into two groups. Students in group on the tutorial support and those in groupltwo do not. In this example, what is the a) Dependent variable b) Independent variable c) Control group d) Experimental group