Solution: Set points A(a, 0) and B(0, b). Let the linear L equation be: x/a+y/b= 1 (intercept type). ∫ The straight line crosses point P(2, 1). ∴ 2/a+ 1/b = 1。 ∴ AB = A+2b。 According to the average inequality formula (x+y 2 √ xy, if and only if x=y is an equal sign), we can get: ∴ AB = A+. ∴ AB ≧ 8。 ∴⊿ Minimum area AOB =( 1/2)ab =4. At this time, a=2b = 8. ∴ A = 4，B = 2。 ∴ The equation of straight line L is