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Diego is solving the equation x2 – 12x = 21

Which value must be added to both sides of the equation to make the left side a perfect -square trinomial?

A

36

B

32

с

144

D

4


Sagot :

Answer:

[tex]36[/tex]

Step-by-step explanation:

Given

[tex]x^2 - 12x = 21[/tex]

Required

Make a perfect square

First, get the coefficient (k) of x

[tex]k = -12[/tex]

Divide by 2

[tex]\frac{k}{2} = \frac{-12}{2}[/tex]

[tex]\frac{k}{2} = -6[/tex]

Square this result:

[tex](\frac{k}{2})^2 = (-6)^2[/tex]

[tex](\frac{k}{2})^2 = 36[/tex]

Hence, 36 when added to the left-hand side makes it a perfect square trinomial