#### Quadratics
**Quadratics:** $x^2 + bx + c = (x+m)(x+n)$ where $mn=c$, $m+n=b$
-**Difference of squares:** $a^2 - b=^2 = (a - b)(a + b)$
+**Difference of squares:** $a^2 - b^2 = (a - b)(a + b)$
**Perfect squares:** $a^2 \pm 2ab + b^2 = (a \pm b^2)$
**Completing the square (monic):** $x^2+bx+c=(x+{b\over2})^2+c-{b^2\over4}$
**Completing the square (non-monic):** $ax^2+bx+c=a(x-{b\over2a})^2+c-{b^2\over4a}$
where
- $x$-intercepts at $x=b,c,d,e$
+
+## Literal equations
+
+Equations with multiple pronumerals. Solutions are expressed in terms of pronumerals (parameters))
+
+## Simultaneous equations (linear)
+
+- Unique solution - lines intersect at point
+- Infinitely many solutions - lines are equal
+- No solution - lines are parallel
+
+Solving in matrix form - use inverse $A^{-1}= {1 \over {ad-bc}}\begin{bmatrix}d & -b \\ -c & a\end{bmatrix}$. $A^{-1}$ exists for infinite solutions or no solutions ($ad-bc=0$), does not exist for unique solutions ($ad-bc \ne 0$).
+Or use `det` on CAS.
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