A的平方+B的平房-6AB等于0
A^2+b^2=6AB
∵A大于B大于0
∴A+B分之B-A的值为=-(A-B)/(A+B)
=-√[(A-B)^2/(A+B)^2]
=-√[(A^2+b^2-2AB)/(A^2+B^2+2AB)]
=-√[(6AB-2AB)/(6AB+2AB)]
=-√(4/8)
=-√2/2