Explanation

The first five positive odd integers are:

1, 3, 5, 7, 9

Let's calculate their sum:

1 + 3 = 4

4 + 5 = 9

9 + 7 = 16

16 + 9 = 25

The sum is:

25

Explanation

A number divisible by 9 but not by 18 must be divisible by 9 but not by 2 (since 18 is a multiple of 2 and 9).

27 is divisible by 9 but not by 18, as 27 ÷ 9 = 3, but 27 ÷ 18 does not result in an integer.

Explanation

(-9) - (-9)

= -9 + 9 (since subtracting a negative is equivalent to adding a positive)

= 0

Explanation

Let's solve the equation:

x + 5 = 3

Subtract 5 from both sides:

x = 3 - 5

x = -2

Explanation

1/50 = 2/100

= 2%

Explanation

The additive inverse of a number is what you add to a number to get zero.

In this context, 1 and -1 are additive inverses of each other, satisfying:

3 + (-1) = 2 and 1 - 3 = -2, showing the concept revolves around opposites in addition.

Explanation

If √x = 7, then squaring both sides gives x = 7² = 49.

So, the value is 49.

Explanation

Given x = 1:

x² + 1/x² = 1² + 1/1²

= 1 + 1

= 2

Explanation

A square has four equal angles, and each angle measures 90 degrees.

It’s a property of all regular quadrilaterals.

Explanation

The radius is half of the diameter, so: 16 cm ÷ 2 = 8 cm.

Radius is the distance from the center of the circle to any point on its edge.