Maths Question (F.4)

odd number 即係單數
eg. 1 , 3, 5 , 7, 9 , 等等都係單數

1^2 係 = 1
3^2 係 = 9
5^2 係 =25
7^ 2 係 =49
9^2 係 =81

1, 9, 25, 49 同 81都係單數啦 !
so the square of any odd number is also an odd number...!

let y be an even number,
then y +1 is a odd number

square of any odd number = (y+1)^2
= y^2 +2y + 1
= y (y +2) + 1

as (y + 2 is an even number, y (y +2 ) is also even number

and y (y +2) + 1 must be an odd number..

1.1x1=1
2.3x3=9
3.5x5=25
4.7x7=49
5.9x9=81
6.11x11=121
7.13x13=169
8.15x15=225
9.17x17=289
10.19x19=361

All of this square are odd no.