Respuesta :
Answer:
i think it is the third one but dont know just an educational geuss
Step-by-step explanation:
The given steps from the derivation of the quadratic formula are:
Step 3: [tex]-c+\frac{b^2}{4a}=a(x^2+\frac{b}{a}x+\frac{b^2}{4a^2})[/tex]
Step 4a: [tex]-c+\frac{b^2}{4a}=a(x+\frac{b}{2a})^2[/tex]
Step 4b: [tex]\frac{-4ac}{4a}+\frac{b^2}{4a}=a(x+\frac{b}{2a})^2[/tex]
The property "converting to a common denominator" justifies step 4b. So, option C: "converting to a common denominator" is correct.
What is the quadratic formula?
The quadratic formula is as follows:
x = [-b ± (√b²+4ac)]/2a
This formula is derived from the quadratic equation [tex]ax^2+bx+c=0[/tex].
What are the steps to derive the quadratic formula?
The standard quadratic equation is [tex]ax^2+bx+c=0[/tex]
Step 1: [tex]ax^2+bx=-c[/tex]
Step 2: Taking 'a' as common
[tex]a(x^2+\frac{b}{a}x)=-c[/tex]
Step 3: Adding [tex]\frac{b^2}{4a}[/tex] on both sides
[tex]-c+\frac{b^2}{4a}=a(x^2+\frac{b}{a}x)+\frac{b^2}{4a}[/tex]
⇒ [tex]-c+\frac{b^2}{4a}=a(x^2+\frac{b}{a}x+\frac{b^2}{4a^2})[/tex]
Step 4a: Factoring the polynomial
[tex]-c+\frac{b^2}{4a}=a(x+\frac{b}{2a})^2[/tex]
Step 4b: Converting to a common denominator
[tex]\frac{-4ac}{4a}+\frac{b^2}{4a}=a(x+\frac{b}{2a})^2[/tex]
⇒ [tex]\frac{(-4ac+b^2)}{4a}=a(x+\frac{b}{2a})^2[/tex]
Step 5: Applying square root (on one side there is a square, so, on the other side it gets ±)
⇒ [tex]\frac{(-4ac+b^2)}{4a^2}=(x+\frac{b}{2a})^2[/tex]
⇒ ±[tex]\sqrt{\frac{(-4ac+b^2)}{4a^2}} =(x+\frac{b}{2a})[/tex]
⇒ [tex]x+\frac{b}{2a}[/tex] = ± [tex]\frac{\sqrt{b^2-4ac} }{2a}[/tex]
step 6: Subtacting [tex]\frac{b}{2a}[/tex] from both the sides
⇒ [tex]x=-\frac{b}{2a}[/tex] ± [tex]\frac{\sqrt{b^2-4ac} }{2a}[/tex]
⇒ x = [-b ± (√b²+4ac)]/2a
Thus, step 4b best explains or justifies the property "Converting to a common denominator".
Learn more about quadratic formula here:
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