Programming $($MATLAB$)$

$1.$ Input: $x,y,$

Output: $x^2-y^2$

$2.$ Input: $a,b$

Output: $|c|=|a+bi|=\sqrt[\phantom{2}]{a^2+b^2}$

Do not use direct build$-$in function.

$3.$ Solve equation $x^2-2px+q=0$

Input: $p,q$

Output: $x_1,x_2$

$4.$ Given $2-$dim array $($matrix$)$ A and $B,$ Find $C=A+B$

Input matrix: A and $B,($same size$)$

Output matrix: A$+$B

Do not use build$-$in functions