Question

Which complex number has an absolute value of 5?
–3 + 4i
2 + 3i
7 – 2i
9 + 4i

Answer 1

the "absolute value" of a complex number is its "length"
use pythagoras. if you have x+ i y, the length is sqr(x^2 + y^2)

it's faster if you know the "triples" of a right triangle: 3,4,5 and 5.12, 13 are often used