I2.1 Let $n=1+3+5+\ldots+31$ and $m=2+4+6 \ldots+32$. If $a=m-n$, find the value of $a$.
I2.2 If Figure $1, A B C D$ is a trapezium, $A B=4 \mathrm{~cm}, E F=a \mathrm{~cm}$, $C D=22 \mathrm{~cm}$ and $F D=8 \mathrm{~cm}$, if the area of $A B E F$ is $b \mathrm{~cm}^{2}$, find the value of $b$.
I2.3 In Figure 2, $\triangle A B C$ is a triangle, $A B=A C=10 \mathrm{~cm}$ and $\angle A B C=b^{\circ}-100^{\circ}$. If $\triangle A B C$ has $c$ axis of symmetry, find the value of $c$.
12.4 Let $d$ be the least real root of the $c x^{\frac{2}{3}}-8 x^{\frac{1}{3}}+4=0$, find the value of $d$.
$$
\begin{aligned}
a & =2+4+6 \ldots+32-(1+3+5+\ldots+31) \\
& =(2-1)+(4-3)+\ldots+(32-31) \\
& =1+1+\ldots+1=16
\end{aligned}
$$

From $A$, draw a line $A P Q$ parallel to $B C$, cutting $F E$ at $P$ and $D C$ at $Q$.
$$
F P=12 \mathrm{~cm}, D Q=18 \mathrm{~cm}
$$
$\triangle A F P \sim \triangle A D Q$
Let $A F=x \mathrm{~cm} \Rightarrow \frac{x}{12}=\frac{x+8}{18}, x=16$
$$
\begin{array}{l}
b=\frac{(4+16) 16}{2}=160 \\
\angle A B C=160^{\circ}-100^{\circ}=60^{\circ}=\angle A C B=\angle B A C
\end{array}
$$
$\triangle A B C$ is an equilateral triangle.
It has 3 axis of symmetry.
$$
3 x^{\frac{2}{3}}-8 x^{\frac{1}{3}}+4=0 \Rightarrow\left(3 x^{\frac{1}{3}}-2\right)\left(x^{\frac{1}{3}}-2\right)=0
$$
$x^{\frac{1}{3}}=\frac{2}{3}$ or 2
$x=\frac{8}{27}$ or 8 , the least real root is $\frac{8}{27}$.