[tex]\bf1.\ \ \it b_5=b_1q^4=3\cdot\Big(\dfrac{b_2}{b_1}\Big)^4=3\cdot\Big(\dfrac{-6}{3}\Big)^4=3\cdot(-2)^4=3\cdot16=48[/tex]
[tex]\bf 2.\ \ \it x_1+x_2-6x_1x_2=-\dfrac{-6}{2}-6\cdot\dfrac{1}{2}=3-3=0[/tex]
[tex]\bf5.\ \ \it AB^2=(x_B-x_A)^2+(y_B-y_A)^2=(9+3)^2+(a-0)^2=144+a^2\ \ \ \ (1)\\ \\ a=13 \Rightarrow a^2=13^2=169\ \ \ \ (2)\\ \\ (1),\ (2) \Rightarrow 144+a^2=169|_{-144} \Rightarrow a^2=25 \Rightarrow a=\pm5[/tex]
[tex]\bf 6.\ \ \Delta ABC-isoscel,\ AB=AC \Rightarrow \widehat C=\widehat B=75^o\\ \\ \widehat A=180^o-2\cdot75^0=30^o\\ \\ Fie\ \ BF\perp AC,\ \ F\in AC,\ \stackrel{T.\angle 30^o}{\Longrightarrow} BF=AC:2=14:2=7\\ \\ \mathcal{A}=\dfrac{AC\cdot BF}{2}=\dfrac{14\cdot7}{2}=7\cdot7=49\ u.\ a.[/tex]
