how to simplify multiplication

The second section how to simplify multiplication

Clarify the idea

The use of addition and subtraction to simplify the operations of multiplication numbers simplified

for example

1x1=1

2x2=4=1x1+1+2

3x3=9=2x2+2+3

4x4=16=3x3+3+4

:

:

21x21=441=20x20+20+21

31x31=961=30x30+30+31

61x61=3721=60x60+60+61

Another example

1x1=1

3x3=9=1x1+4x2

4x4=16=2x2+4x3

6x6=36=4x4+4x5

32x32=1024=30x30+4x31

62x62=3844=60x60+4x61

Numbers ending by number 0

10x10=100

Numbers ending by number 5

5x5=25

15x15=1x1+1<25>=225

25x25=2x2+2<25>=625

35x35=3x3+3<25>=1225

125x125=12x12+12<25>=15625

<136x136=135x135+<135+136

=18225 + 271=18496

137x137=135x135+4x136

18769= 18225+544=

138x138=140x140-4x139

19044=556 -19600=

<139x139=140x140-<140+139

19321=19600-279=

143x143=145x145-4x144

14x14+14 <25> - 4x144

20449=21025-576=