Question

Which is equivalent to (2-5i)(-2+5i)

Answer 1

$(2-5i)(-2+5i)=\\ -(2-5i)^2=\\ -(4-20i-25)=\\ -(-21-20i)=\\ 21+20i$

Answer 2

= -4 + 10i + 10i -25i^2 = -4 + 20i + 25 = 21 + 20i, because i^2 = -1.