1.
[tex]\it x_M=\dfrac{x_A+x_B}{2} \Rightarrow -4=\dfrac{a-2}{2} \Rightarrow -8=a-2|_{+2} \Rightarrow a=-6 \Rightarrow A(-6,\ 3)\\ \\ \\ y_M=\dfrac{y_A+y_B}{2} \Rightarrow 1=\dfrac{3+b}{2} \Rightarrow 2=3+b|_{-2} \Rightarrow b=-1 \Rightarrow B(-2,\ -1)[/tex]
[tex]\it AB^2=(x_B-x_A)^2+(y_B-y_A)^2=(-2+6)^2+(-1-3)^2=4^2+(-4)^2=\\ \\ =16+16=32 \Rightarrow AB=\sqrt{32}=\sqrt{16\cdot2}=4\sqrt2\ cm[/tex]
2.
Fie S = suprafața totală.
[tex]\it (\dfrac{S}{6}+\dfrac{S}{6}-10)\cdot3=\dfrac{S}{2} \Rightarrow \dfrac{S}{2}+\dfrac{S}{2}-30=\dfrac{S}{2} \Rightarrow \dfrac{S}{2}+\dfrac{S}{2}-\dfrac{S}{2}=30 \Rightarrow\\ \\ \\ \Rightarrow \dfrac{S}{2}=30|_{\cdot2} \Rightarrow S=60\ ha[/tex]
