δ=r1+r2−A\rm{\delta=r_{1}+r_{2}-A}δ=r1+r2−A
δ=r1−r2−A\rm{\delta=r_{1}-r_{2}-A}δ=r1−r2−A
δ=i1+i2−A\rm{\delta=i_{1}+i_{2}-A}δ=i1+i2−A
δ=i1−i2−A\rm{\delta=i_{1}-i_{2}-A}δ=i1−i2−A
