r2+52(cosθ+sinθ)r+21=0r^{2}+5 \sqrt{2}(\cos \theta+\sin \theta) r+21=0r2+52(cosθ+sinθ)r+21=0
r2−52(cosθ+sinθ)r−21=0r^{2}-\frac{5}{\sqrt{2}}(\cos \theta+\sin \theta) r-21=0r2−25(cosθ+sinθ)r−21=0
r2+52(cosθ+sinθ)r−21=0r^{2}+5 \sqrt{2}(\cos \theta+\sin \theta) r-21=0r2+52(cosθ+sinθ)r−21=0
r2+52(cosθ+sin2θ)r+21=0r^{2}+\frac{5}{\sqrt{2}}\left(\cos \theta+\sin ^{2} \theta\right) r+21=0r2+25(cosθ+sin2θ)r+21=0
r2−52(cosθ+sinθ)r+21=0r^{2}-5 \sqrt{2}(\cos \theta+\sin \theta) r+21=0r2−52(cosθ+sinθ)r+21=0