b, \(\Delta=\left(-8\right)^2-4.1.7=64-28=36>0\)
\(x_1=\dfrac{8+6}{2}=7,x_2=\dfrac{8-6}{2}=1\)
\(c,\Delta=\left(-6\right)^2-4.1.\left(-3\right)=36+12=48>0\)
\(x_1=\dfrac{6+4\sqrt{3}}{2}=3+2\sqrt{3},x_2=\dfrac{6-4\sqrt{3}}{2}=3-2\sqrt{3}\)
\(d,\Delta=\left(-6\right)^2-4.1.\left(-7\right)=36+28=64>0\)
\(x_1=\dfrac{6+8}{2}=7,x_2=\dfrac{6-8}{2}=-1\)