Question

21у² – 2y - 3 =0 помогите решить​

Answer 1

Ответ:

21у²-2у-3=0

D=(-2)²-4*21*(-3)=4+252=256

x1,2=-(-2)±√256/2*21=2±16/42

x1=2-16/42=-14/42=-1/3

x2=2+16/42=18/42=3/7

Объяснение:

Answer 2

$21y^{2} -2y-3=0;\\a=21;b=-2;c=-3.\\D=b^{2} -4ac=(-2)^{2} -4*21*(-3)=4+252=256;\\x_{1,2} =\dfrac{-b \pm\sqrt{D} }{2a} ;\\x_{1} =\dfrac{-(-2-\sqrt{256}) }{2*21} =\dfrac{2-16}{42} =\dfrac{-14}{42} =-\dfrac{1}{3} ;\\x_{2} =\dfrac{-(-2+\sqrt{256} )}{2*21} =\dfrac{2+16}{42} =\dfrac{18}{42} =\dfrac{3}{7} .$