Cho biểu thức P= ( 1+ căn a/ a+1): ( 1/ căn a-1- 2 căn 1/ acăn a + căn a- a-1 . a) Rút gọn P.

P=1+aa+1:1a−1−2aaa+a−a−1

=1+aa+1:1a−1−2aa+1a−1

ĐKXĐ: a ≥ 0; a ≠ −1; a ≠ 1.

Ta có: P=1+aa+1:1a−1−2aa+1a−1=a+a+1a+1:a+1a+1a−1−2aa+1a−1=a+a+1a+1:a−2a+1a+1a−1=a+a+1a+1:a−12a+1a−1=a+a+1a+1:a−1a+1=a+a+1a+1a+1a−1=a+a+1a−1