Question

Which expression is equivalent to16x2+81?
1.
(4x−9i)2
2.
(4x+9i)(2x+3i)(2x−3i)
3.
(4x+9i)(4x−9i)
4.
(4x+9i)2

Answer 1

16*X² +81

The answer is 3

(4x+9i)(4x−9i) = (4x+9i)*4x -9i((4x+9i)) = 16x2 +36i -36i -81i2 = 16x² -81(-1)

= 16x² +81