Respuesta :
Answer:
(C)Converting to a common denominator
Step-by-step explanation:
Given some of the steps in the derivation of the quadratic formula below:
[tex]\text{Step 3:} -c + \dfrac{b^2}{4a}=a(x^2+ \dfrac{b}{a}x+ \dfrac{b^2}{4a^2})\\\\\text{Step 4a:} -c + \dfrac{b^2}{4a}=a(x+\dfrac{b}{2a})^2\\\\\text{Step 4b:} \dfrac{-4ac}{4a}+ \dfrac{b^2}{4a}=a(x+\dfrac{b}{2a})^2[/tex]
Step 4b is derived from Step 4a by converting the left-hand side to a common denominator 4a.
Therefore, that which best explains or justifies Step 4b is:
(C)Converting to a common denominator