jika akar akar persamaan kuadrat 2x²-3x-9=0 adalah x1 dan x2 maka besar x1 ²+x2² adalaha.11 1/4b.6 3/4c.2 1/4d. -6 3/4e. -11 1/4

[tex] {2x}^{2} - 3x - 9 = 0 \\ a = 2 \: \: \: b = - 3 \: \: \: c = - 9 \\ {x1}^{2} + {x2}^{2} \\ = {(x1 + x2)}^{2} - 2x1x2 \\ = ( \frac{ -b}{a} )^{2} - 2( \frac{c}{a} ) \\ = (\frac{3}{2})^{2} - 2( \frac{ - 9}{2} ) \\ = \frac{9}{4} + \frac{18}{2} \\ = \frac{9 + 36}{4} \\ = \frac{45}{4} \\ = 11 \frac{1}{4} [/tex]