20 1 1! ÷20 12=20 1 1! ÷(20 1 1! *20 12)=20 1 1! ÷20 1 1! ÷20 12= 1/20 12

The second question:

Assuming that the numerator and denominator of the formula are multiplied by (√5+ 1) at the same time, then

(√5+ 1)/(√5- 1)=(√5+ 1)^2 / [(√5+ 1)(√5- 1)]=(3+√5)/2

From common sense, we know that √5 is about 2.2, so 3+√5 is about 5.2.

The integer part of (3+√5)/2 is 2, and a=2.

The fractional part is (3+√5)/2-2=(√5- 1)/2 and b=(√5- 1)/2.