Which of the following is not always true?

Options

A. `|vec(a) + vec(b)|^(2) = |vec(a)|^(2) + |vec(b)|^(2) " if " vec(a) and vec(b)` are perpendicular to each other
B. `|vec(a) + lamda vec(b)| ge |vec(a)|` for all `lamda in R` if `vec(a) and vec(b)` are perpendicular to each other
C. `|vec(a) + vec(b)|^(2) + |vec(a) - vec(b)|^(2) = 2(|vec(a)|^(2) + |vec(b)|^(2))`
D. `|vec(a) + lamda vec(b)| ge |vec(a)| " for all " lamda in R` if `vec(a)` is parallel to `vec(b)`

Answer

D