Question

.a) (x+1)(y+1)=xy+x+y+_____


b) Find 21×31 using the
above principle ​

Answer 1

Answer:

1. a) 4xy b) 21=11 square - 10 square
2. 11 square substracted by 10 square
3. 11 square=121
4. 10 square=200