Question

Subtract the square of 21 from the square of 22 without actually calculating the squares. ​

Answer 1

Answer:

Given,

We need to Subtract the square of 21 from the square of 22 without actually calculating the squares.

Using the formula

${x}^{2} - {y}^{2} = (x + y)(x - y)$

We get.....

$= > {(22)}^{2} - {(21)}^{2} \\ = > (22 + 21)(22 - 21) \\ = > 43 \times 1 \\ = > 43.$

Answer 2

Answer:

we can write 21 as 20+1

if square$(20+1)^{2}$

we can write 22 as 20+2

if square

$(20+2)^{2}$

by using identity

$(x+y)^{2} =x^{2} +2xy+y^{2}$

$(22)^{2} -(21)^{2}$$20^{2} +2*20*2+2^{2} -(20^{2} +2*20*1+1^{2} )\\=400+80+4-(400+40+1)\\=400+84-400-40-1$

=43 is the correct answer