(B²-A²)/(A²-AB)÷[A+(2AB+B²）/A]×1/(1+B)/A
=-(A+B)/A÷(A+B)²/A×A/(1+B)
=-A/(1+B)(A+B)
=-(√2+√3)/(1+√2-√3)(√2+√3+√2-√3)
=-(√2+√3)/2√2(1+√2-√3)
=-(√2+√3)(1-√2+√3)/2√2(1+√2-√3)(1-√2+√3)
=-(√2+√3)(1-√2+√3)/2√2(1+1+√6)
=-(√2+√3)(1-√2+√3)/2√2×√2(√2+√3)
=-(1-√2+√3)/4