Đáp án+Giải thích các bước giải:
`a)ĐKXĐ:{(b>=0),(1-sqrtb ne 0),(1-b ne 0):}`
`<=>{(b>=0),(b ne 1):}`
`a)B=(1+sqrtb)/(1-sqrtb)-(1-sqrtb)/(1+sqrtb)+(4sqrtb)/(1-b)`
`B=(1+sqrtb)^2/((1-sqrtb)(1+sqrtb))+(4sqrtb)/(1-b)`
`B=(b+2sqrtb+1-b+2sqrtb-1+4sqrtb)/((1-sqrtb)(1+sqrtb))`
`B=(8sqrtb)/(1-b)`
`b)B> -1`
`<=>B+1>0`
`<=>(8sqrtb+1-b)/(1-b)>0`
`<=>(b-8sqrtb-1)/(b-1)>0`
`<=>((sqrtb-4)^2-17)/(b-1)>0`
`<=>((sqrtb-4-sqrt{17})(sqrtb-4+sqrt{17}))/(b-1)>0`
Mà `sqrtb-4+sqrt{17}>0`
`<=>(sqrtb-4-sqrt{17})/(b-1)>0`
`<=>[({(sqrtb-4-sqrt{17}>0),(b-1>0):}),({(sqrtb-4-sqrt{17}<0),(b-1<0):}):}`
`<=>[(sqrtb>4+sqrt{17}),(b<1):}`
`<=>[(b>33+8sqrt{17}),(b<1):}`