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c5d14cb917
FIR draft
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2025-01-23 10:34:06 -08:00
ede934369b
Add local typst packages
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2025-01-23 10:29:13 -08:00
3b41ea714a
Added "Tropical Polynomials" handout 2025-01-23 10:29:07 -08:00
2 changed files with 8 additions and 10 deletions

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@ -62,8 +62,7 @@ Let's expand $#sym.RR$ to include a tropical additive identity.
#problem()
Do tropical additive inverses exist? \
#note([
Is there an inverse $y$ for every $x$ so that $x #tp y = #sym.infinity$? \
Remember that $#sym.infinity$ is the additive identity.
Is there an inverse $y$ for every $x$ so that $x #tp y = #sym.infinity$?
])
#solution([
@ -278,7 +277,7 @@ Fill the following tropical addition and multiplication tables
#problem()
Expand and simplify $f(x) = (x #tp 2)(x #tp 3)$, then evaluate $f(1)$ and $f(4)$ \
#hint([Adjacent parenthesis imply tropical multiplication])
Adjacent parenthesis imply tropical multiplication
#solution([
$

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@ -20,7 +20,7 @@ for some nonnegative integer $n$ and coefficients $c_0, c_1, ..., c_n$. \
The _degree_ of a polynomial is the largest $n$ for which $c_n$ is nonzero.
#theorem()
The _fundamental theorem of algebra_ states that any non-constant polynomial with real coefficients
The _fundamental theorem of algebra_ implies that any non-constant polynomial with real coefficients
can be written as a product of polynomials of degree 1 or 2 with real coefficients.
#v(2mm)
@ -30,8 +30,8 @@ can be written as $(x^2 + 2x+5)(x-2)(x+4)(x+4)$
#v(2mm)
A similar theorem exists for polynomials with complex coefficients. \
These coefficients may be found using the _roots_ of this polynomial. \
As you already know, there are formulas that determine the roots of quadratic, cubic, and quartic #note([(degree 2, 3, and 4)]) polynomials. There are no formulas for the roots of polynomials with larger degrees---in this case, we usually rely on appropriate roots found by computers.
These coefficients may be found using the roots of this polynomial. \
As it turns out, there are formulas that determine the roots of quadratic, cubic, and quartic #note([(degree 2, 3, and 4)]) polynomials. There are no formulas for the roots of polynomials with larger degrees---in this case, we usually rely on approximate roots found by computers.
#v(2mm)
In this section, we will analyze tropical polynomials:
@ -100,7 +100,7 @@ In other words, find $r$ and $s$ so that
),
)
#note([Naturally, we will call $r$ and $s$ the _roots_ of $f$.])
we will call $r$ and $s$ the _roots_ of $f$.
#solution([
Because $(x #tp r)(x #tp s) = x^2 #tp (r #tp s)x #tp s r$, we must have $r #tp s = 1$ and $r #tm s = 4$. \
@ -116,8 +116,7 @@ In other words, find $r$ and $s$ so that
#v(1fr)
#problem()
Can you see the roots of this polynomial in the graph? \
#hint([Yes, you can. What "features" do the roots correspond to?])
How can we use the graph to determine these roots?
#solution([The roots are the corners of the graph.])
@ -317,7 +316,7 @@ into linear factors.
#v(2mm)
Whenever we say "the roots of $f$", we really mean "the roots of $accent(f, macron)$." \
Also, $f$ and $accent(f, macron)$ might be the same polynomial.
$f$ and $accent(f, macron)$ might be the same polynomial.
#problem()
If $f(x) = a x^2 #tp b x #tp c$, then $accent(f, macron)(x) = a x^2 #tp B x #tp c$ for some $B$. \