Решите. 2х²-5х+2=0. х²-6х-8=0. х²+5х-9=0.

$1)2x {}^{2} - 5x + 2 = 0$
D=b²-4ac
D= $- 5 {}^{2} - 4 \times 2 \times 2 = 25 - 16 = 9$
$x1 = \frac{5 + 3}{2 \times 2} = \frac{8}{4} = 2$
$x2 = \frac{5 - 3}{4} = \frac{1}{2} = 1.5$
$2)x {}^{2} - 6x - 8 = 0$
D= $36 + 32 = 68$
$x1 = \frac{6 + 2 \sqrt{17} }{2} = 3 + 2 \sqrt{17}$
$x2 = \frac{6 - 2 \sqrt{17} }{2} = 3 - 2 \sqrt{17}$
$3)x { + 5x}^{2} - 9 = 0$
D= $25 + 4 \times 9 = 61$
$x1 = \frac{ - 5 +7 \sqrt{12} }{2} \\ x2 = \frac{ - 5 - 7 \sqrt{12} }{2}$