The concept of reciprocal mathematics in the sixth grade of primary school! Kneel and beg for urgent use within 48 hours. The teacher wants me to give a lecture tomorrow! )

Two rational numbers whose product is 1 are reciprocal (reciprocal 1).

Two rational numbers whose product is-1 are reciprocal.

If A and B are reciprocal, AB =1;

If A and B are negative reciprocal, ab=- 1.

Note: (1) Zero has neither reciprocal nor negative reciprocal.

(2) When a ≠ 0, the reciprocal of a is.

(3) To find the reciprocal of a fraction, just reverse the numerator and denominator of this fraction.

(4) The reciprocal of a positive number is positive, and the reciprocal of a negative number is still negative.

(5) The number whose reciprocal equals itself is 1.