Your friend multiplied complex numbers and expressions as shown. find the error in your friends work. then factor the expression correctly. show work .

(4-7i)(4+7i)=16+28i-28i+49i^2
=16-49
=-33

  = 16+49 = 65

Step-by-step explanation:

The error is at the end of the first line. (-7i)(7i) = -49i² ≠ +49i².

The correct work is ...

  (4-7i)(4+7i)=16+28i-28i-49i^2

  = 16+49

  = 65

check the picture below.

well, the angle at the vertex d is clearly not a right-angle, let's check for the one at the vertex f which does look like,   however if it's indeed, that means ef is perpendicular to df, in which case their slopes will be negative reciprocal of each other.

so the negative reciprocal of the slope of ef is 1, however the slope of df is not 1, is 1/2, so nope, they're not perpendicular lines.