Lesson 23

Polynomial Identities (Part 1)

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Problem 1

Select all the identities:​​​​

A:

\((x+2)^3 = x^3 + 8\)

B:

\((x^6 + x) = (x-1)(x^5 + x^4 + x^3 + x^2 + x)\)

C:

\((x^2 - 1)(x^4 + x^2 + 1) = x^6 - 1\)

D:

\((x+1)^4 = x^4 + x^3 + x^2 + x + 1\)

E:

\((x+1)(x^4 - x^3 + x^2 - x + 1) = x^5+1\)

F:

\((x^3 - 1)(x^3 + 1) = x^6 - 1\)

Problem 2

Is \(2(x+1)^2 = (2x+2)^2\) an identity? Explain or show your reasoning.

Problem 3

Mai is solving the rational equation \(5 = \frac{2+7x}{x}\) for \(x\). What move do you think Mai would make first to solve for \(x\)? Explain your reasoning.

Problem 4

For $x$-values of 0 and -2, $(x^5+32) = (x+2)^5$. Does this mean the equation is an identity? Explain your reasoning.

Problem 5

Clare finds an expression for \(S(r)\) that gives the surface area in square inches of any cylindrical can with a specific fixed volume, in terms of its radius \(r\) in centimeters. This is the graph Clare gets if she allows \(r\) to take on any value between -1.2 and 3.

  1. What would be a more appropriate domain for Clare to use instead?
  2. What is the approximate minimum surface area for her can?
graph of y = S of r. vertical asymptote at x = 0. x intercept at about -1. function decreasing to the left of asymptote. function decreases until y = 10 and then increases to the right of asymptote.
(From Algebra2, Unit 2, Lesson 16.)

Problem 6

Which values of \(x\) make \(\frac{3x+1}{x}=\frac{1}{x-3}\) true?

(From Algebra2, Unit 2, Lesson 22.)