What number must you add to complete the square x^2-16=23

For this case we must complete squares:

We add the square of half the coefficient of the term "x",

on both sides of the equation:

According to the perfect square trinomial we have:

Rewriting the expression we have:

rectangle: 9 1/8 x 4 1/9 = 37 37/72in

parallelogram: b times h= 10.3 x 6.2 = 63.86

trapezoid: a+b/2 times h= 42.5

volume of prism: l times w times h= 36