Solution: 1, simplify (a-2)(a? +2a+4)-a(a-4)？ +(2a+ 1)(2a- 1) and get 12a? -16a-9, and then substitute a= negative half, and the value of f(a) can be obtained as 2.

2. Can you square both sides of the formula x-x 1=3: X? +( 1/x？ )-2=9,

So: x? +x？ The value of 1 is 1 1.