Complete the square
y^2-4y+?

y

2

−

4

y

Explanation:

y

2

−

4

y

Use the form  

a

x

2

+

b

x

+

c

, to find the values of  

a

,  

b

, and  

c

.

a

=

1

,

b

=

−

4

,

c

=

0

Consider the vertex form of a parabola.

a

(

x

+

d

)

2

+

e

Substitute the values of  

a

and  

b

into the formula  

d

=

b

2

a

.

d

=

−

4

2

(

1

)

Simplify the right side.

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d

=

−

2

Find the value of  

e

using the formula  

e

=

c

−

b

2

4

a

.

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e

=

−

4

Substitute the values of  

a

,  

d

, and  

e

into the vertex form  

a

(

x

+

d

)

2

+

e

.

(

y

−

2

)

2

−

4

-15 and 8

Step-by-step explanation:

-15 × 8 = -120

-15 + 8 = -7