For Question number 1:
The function f(x) is a difference of squares. Is exactly what its name says, you take 2 squared quantities like x² and z² or a square of a number like 36 or 25, then put a minus sign between them. So
f(x) = x² - 49 =factors to=> (x-7)(x+7) or
f(x) = 64 - x² =factors to=> (8+x)(8-x) or
f(x) = x² - k² =factors to=> (x+k)(x-k) and so on.....
this is factored by taking the root of each term and rewriting them as a sum and difference.
The function g(x) is a sum of squares. This is the same as above but with a + sign in between
g(x) = x² + 25 or
g(x) = 81 + x² or
g(x) = x² + p² and so on.....
These terms do not factor.
The function h(x) is a perfect square trinomial.
A perfect square trinimial is created by taking x (at any power) and adding or subtracting it to a number or letter, then squaring the whole quantity, and as a last, optional step, you expand this quantity.
h(x) = (x+3)² = x² + 6x +9 or
h(x) = (2x-5)² = 4x² - 20x + 25 or
h(x) = (x² - t)² = x^4 - 2tx² + t² and so on........
The function j(x) can only have a GCF factored out of it.
Here the equation must have an x in it, the x can be any power, and only the coefficients of the x's can be factored out, and there may be one number only term that also factors with the coefficients, like
j(x) = 14x² + 21x - 7 =factors to=> 7(2x² + 3x - 1) or
j(x) = 10x - 25t + 15 =factors to=> 5(2x² - 5t + 3) or
j(x) = 64x³ + 16x² - 8x + 24 =factors to=> 8(8x³ + 2x² - x + 3) or
j(x) = 64x³ + 16x² - 8x =factors to=> 8x(8x² + 2x - 1) and so on ......