Question

determine the value of a-b, if a+b=5 and ab=4​

Answer 1

Use substitution

A=5-b

b(5-b)=4

5b-b^2=4

b^2–5b+4=0

Factor

(b-4)(b-1)=0

b=4,1

A is therefore equal to 4 or 1.

A-b can be either 4–1=3 or 1–4=-3