Another maths qu? ?

Question

when Y is odd, explain why (y+5)(y-1) is an even number.

Answer 1

(y+5)(y-1)

=y^2-y+5y-5

y^2+4y-5

the square of odd number is an odd number, also any odd number multiplied by 4 would give an even number . so if you inpu 3 instead of y

you will get

3^2+4(3)-5

9+12-5

16

Answer 2

u have to times the 2 brackets to gether eg: y=3

(3+5)(3-1)

8x3= 24

Answer 3

If you add two odd numbers, their sum is even so y+5 is even.

If you subtract two odd numbers, their difference is even so y-1 is even.

When you multiply two even numbers, their product is even so

(y+5)(y-1) is even.

Answer 4

Adding or subtracting on odd number from another odd number will always give you an even number. Pick any odd number for y, subtracting 1 or adding 5 will always give you an even number, and multiplying two even numbers will always give you an even number.

ex. y= 7

(7+5)(7-1)= (12) (6)= 84

ex. y= 15

(15+5) (15-1)= (20)(14)= 280

Answer 5

when y is odd so sum of 2 odds is even

so y+5=even

substraction of 2 odds is also even.

y-1 = even

so we have (even)*(even)  =(y+5) (y-1)

multiplication of 2 even numbers is always even

Answer 6

If y is odd, it can be expressed as 2n + 1 for some integer n, regardless of whether n is odd or even.

(y+5)(y-1) = (2n+1+5)(2n+1-1) = (2n+6)(2n) = 2 (2n^2 + 6n) is a multiple of 2 so is even.