Select all equations that can result from adding these two equations or subtracting one from the other. A. \( -2 x-4 y=8 \) B. \( -2 x+6 y=8 \) C. \( 4 x-4 y=16 \) D. \( 4 x+4 y=16 \) E. \( 2 x-6 y=-8 \) F. \( 5 x-4 y=28 \)

Los likningen \( 2^{x}=7 \)

9. \( \square^{2}-50=-1 \)

b) \( \mathrm{C}_{23}^{25}=\frac{\mathrm{P}_{2}^{25}}{2!} \)

Find the average rate of change of the function \( f(x)=-2 x^{2}-2 x+1 \), from \( x=-2 \) to \( x=1 \). Note, the directions are equivalent to "Find the average rate of change over the interval \( [-2,1] \) ". Average rate of change \( =\square \)

Плоскость \( \alpha \) пересекает стороны \( A C \) и \( B C \) треугольника \( A B C \) в точках \( A_{1} \) и \( B_{1} \) соответственно, так что \( A A_{1}: A_{1} C=B B_{1}: B_{1} C=1: 3 \). Докажите, что \( A B \| \alpha \) и найдите \( A_{1} B_{1} \), если \( A B=12 \).