Question

Через D=b^2-4ac 8 класс

Answer 1

Ответ и объяснение:

$4)\ 21y^2-2y-3=0\\D = (-2)^2-4*21*(-3)=4+252=256\\y_{1/2} =\dfrac{2б16}{42}\\\\y_1=\dfrac{2-16}{42} = -\dfrac{14}{42} = -\dfrac{1}{3}\\\\y_2=\dfrac{2+16}{42} = \dfrac{18}{42} = \dfrac{3}{7}$

$5)\ x^2 + 8x-13=0\\D = 8^2-4*1*(-13) = 64+52=116\\x_{1/2} =\dfrac{-8б\sqrt{116} }{2} = \dfrac{-8б\sqrt{4*29} }{2} =\dfrac{-8б2\sqrt{29} }{2} = -4б\sqrt{29}$

$6)\ 2x^2-4x-17=0\\D = (-4)^2 - 4 * 2 * (-17) = 16+136=152\\x_{1/2} =\dfrac{4б\sqrt{152} }{4} =\dfrac{4б\sqrt{4*38} }{4} =\dfrac{4б2\sqrt{38} }{4} =\dfrac{2б\sqrt{38} }{2}$