[tex]8y^2-22y-21 =0 \\ \\a=8, \ \ b=-22, \ \ c=-21\\ \\\Delta = b^{2}-4ac = (-22)^{2}-4*8* (-21)= 484+672=1156 \\ \\y_{1}=\frac{-b-\sqrt{\Delta }}{2a} =\frac{22- \sqrt{1156}}{2*8}=\frac{22-34}{16}=\frac{-12}{16}= -\frac{3}{4}\\ \\y_{2}=\frac{-b+\sqrt{\Delta }}{2a} =\frac{22+ \sqrt{1156}}{2*8}=\frac{22+34}{16}=\frac{56}{16}= \frac{7}{2}=3\frac{1}{2}[/tex]
