Question

( a-b)^2 ≠ 4^2 + 5^2

Answer 1

$$(a+b)^2≠4^2 + 5^2$$

Answer 2

try expanding the Left-hand-side first. so the equation in terms of variables is:

Answer 3

$$(a+b)^2 \neq (a)^2 + (b)^2 $$

Answer 4

In particular, this is because:

$$(a + b)^2 = (a + b)(a + b)$$

Which evaluates to something very different than $$a^2 + b^2$$.