Number systems

Which of these is a rational number?

• 1 pi
• 2 The square root of 5
• 3 0.75
• 4 The square root of 3

i to the power 4 equals:

• 1 i
• 2 -1
• 3 1
• 4 -i

(1 + i)(1 - i) equals:

• 1 -2
• 2 0
• 3 2
• 4 1 - i2

The modulus of 3 + 4i is:

• 1 5
• 2 1
• 3 25
• 4 7

The multiplicative inverse of 2 + i is:

• 1 1 / 2
• 2 (2 + i) / 5
• 3 (2 - i) / 5
• 4 2 - i