akar-akar persamaan x²-ax+2a-7 =0,x1 dan x2. jika 2x1-x2 =7 nilai a adalah

[tex]x1 + x2 = a \\ 2x1 - x2 = 7 \\ 3x1 = a + 7 \\ x1 = \frac{a + 7}{3} \\ x2 = a - ( \frac{a + 7}{3}) = \frac{3a - a - 7}{3} = \frac{2a - 7}{3} = \frac{x1.x2}{3} = \\ 3x2 = x1.x2 \\ x1 = 3 \\ a + 7 = 9 \\ a = 2[/tex]