August 19, 2007
This session is based on the material in section 2.2 of Kelley's "The Humongous Book of Calculus Problems"
The section presents a series of problems involving simplifying polynomial expressions involving the four basic arithmetic operations
Problem 2.11

In[21]:=

Simplify[3 (x^2 - 5xy + 6y^2) - 5 (x^2 + 4xy - 1)]

Out[21]=

5 - 2 x^2 - 35 xy + 18 y^2

In[22]:=

Simplify[(-2x^2) (y - 4) + x (x + 6) - 4 (3x - y) + (7y^2) (x + 1) + 6y (y - 9) - 3 (y + 5x)]

Out[22]=

x^2 (9 - 2 y) + y (-53 + 13 y) + 7 x (-3 + y^2)

In[23]:=

FullSimplify[(-2x^2) (y - 4) + x (x + 6) - 4 (3x - y) + (7y^2) (x + 1) + 6y (y - 9) - 3 (y + 5x)]

Out[23]=

x^2 (9 - 2 y) + y (-53 + 13 y) + 7 x (-3 + y^2)

There is a difference in the ordering of the terms between Mathematica and Kelley. Thus it is apparent that there is no universal standard for this. Interesting.

In[24]:=

Simplify[(a - 3b)^2]

Out[24]=

(a - 3 b)^2

In[25]:=

Expand[(a - 3b)^2]

Out[25]=

a^2 - 6 a b + 9 b^2

In[26]:=

Expand[(2x - y) (x + 5y - 1)]

Out[26]=

-2 x + 2 x^2 + y + 9 x y - 5 y^2

In[27]:=

(2x^3 - 5x^2 + 9x - 8)/(x + 3)

Out[27]=

(-8 + 9 x - 5 x^2 + 2 x^3)/(3 + x)

In[28]:=

Simplify[(2x^3 - 5x^2 + 9x - 8)/(x + 3)]

Out[28]=

(-8 + 9 x - 5 x^2 + 2 x^3)/(3 + x)

In[29]:=

FullSimplify[(2x^3 - 5x^2 + 9x - 8)/(x + 3)]

Out[29]=

(-8 + x (9 + x (-5 + 2 x)))/(3 + x)

In[30]:=

Evaluate[(2x^3 - 5x^2 + 9x - 8)/(x + 3)]

Out[30]=

(-8 + 9 x - 5 x^2 + 2 x^3)/(3 + x)

In[31]:=

PolynomialQuotient[(2x^3 - 5x^2 + 9x - 8), (x + 3), x]

Out[31]=

42 - 11 x + 2 x^2

In[32]:=

PolynomialRemainder[(2x^3 - 5x^2 + 9x - 8), (x + 3), x]

Out[32]=

-134

Mathematica is able to work with some very complex algebraic expressions, but I do not see the value in much of this. I much prefer being able to carry out such operations by hand where I can see the logic behind the various steps.
This has been interesting though as I now see the difference between using the computer to perform symbolic operations and doing them by hand.
Addition and subtraction of polynomials is straight forward. Multiplication uses the command Expand and division requires two separate steps: PolynomialQuotient and PolynomialRemainder.


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