Additive commutative law's laws of addition and association, multiplication and exchange, multiplication and association, multiplication and distribution.

The letters a+b = b+a (a+b)+c = a+(b+c) a× b = b× a (a× b )× c = a× (b× c) (a+b )× c = ab+AC.

2、( 1)+2 1 (2)( 125×8) (3)5×4 (4) (49+ 15_+_ 1__)×38

3 、= >; = & lt

Second, * * * *

Three. 1.C 2。 A 3。 B 4。 B

Four. ××××

Verb (abbreviation of verb)1,165 96 80130010 20 30001584

2、5400 178 5 700 3366 5700

6. 1, additive commutative law 2, multiplicative commutative law 3, additive associative law.

4. Multiplicative associative law 5. fenpeilv

Seven. 1, = 2, = found: a ÷ c+b ÷ c = (a+b) ÷ c.

Eight, 1,125× 79+125× 21=12500.

2、32× 15+ 19=499

3、(777-560)÷7=-3 1

IX. 1, 188-57-43=88 (page 1)

2, 48+2 10+52=3 10 (km)