Решение задания приложено
1)3х^2-28х+9=0
D = b^2 - 4 * a * c = (-28)^2 - 4 * (3) * (9) = 676
x1 = (-b +
sqrt(D)) / (2*a)
x2 = (-b -
sqrt(D)) / (2*a)
x1 = 9
x2 = 1/3
2)2х^2-8х+11=0
D = b^2 - 4
* a * c = (-8)^2 - 4 * (2) * (11) = -24
<span> ___</span>
<span> I*\/ 6 </span>
x1 = 2 +
-------
<span>2 </span>
<span> ___</span>
<span> I*\/ 6 </span>
x2 = 2 -
-------
<span> 2
</span>
3)16х^2-8х+1=0
D =
0, то корень всего один.
x = -b/2a =
--8/2/(16)
x = 1/4
4)7х^2-21=0
D = b^2 - 4
* a * c =
(0)^2 - 4 *
(7) * (-21) = 588
<span> ___</span>
x1 = \/ 3
<span> ___</span>
<span>x2 = -\/ 3</span>