Answer:
a.
x²+3x-4
doing middle term factorization
x²+(4-1)x-4
x²+4x-x-4
x(x+4)-1(x+4)
( x+4)(x-1)
b.
x²-2x-3
x²-3x-x-3
x(x-3)-1(x-3)
(x-3)(x-1)
c.
x²+2x-8
x²+4x-2x-8
x(x+4)-2(x+4)
(x+4)(x-2)
