# Algebra B

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x^2 - 5/2x + 25/16 = -4 + 25/16
= (x-5/4)^2 = -64/16 + 25/16
= (x-5/4)^2 = -39/16

Would someone please explain how we arrived at

(x - 5/4)^2 = -64/16 + 25/16 from

x^2 - 5/2x + 25/16 = -4 + 25/16

• Algebra B -

Which side (left or right) is puzzling?

• Algebra B -

The left, Thanks

• Algebra B -

OK,
(x-5/4)^2
= (x-5/4)(x-5/4)
multiplying (remember FOIL--first, outer, inner, last)

= x^2 -(5/4)(x) - (5/4)(x) + (5/4)^2
= x^2 - (10/4)(x) + (5^2)/(4^2)
= x^2 -(5/2)(x) + (25)/(16)

Does that help?

• Algebra B -

Oh, reverse FOIL!

Thank you.

• Algebra B -

You're welcome, but I am not sure what you mean by reverse FOIL.

First terms: x and x
Outer terms: x and -5/4
Inner terms: -5/4 and x
Last terms : -5/4 and -5/4

I just want to be sure you have a good understanding about the order.

• Algebra B -

Yes, You explained it very well. Thanks for taking the time.

• Algebra B -

You are very welcome.

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