1. We define $a \star b=a \times a-b \times b$, then $3 \star 2+4 \star 3+5 \star 4+\cdots+20 \star 19=$
【Answer】 396
【Key Point】Definition of New Operation
【Analysis】
$$
\begin{aligned}
\text { Original expression } & =(3 \times 3-2 \times 2)+(4 \times 4-3 \times 3)+(5 \times 5-4 \times 4)+\cdots+(20 \times 20-19 \times 19) \\
& =3 \times 3-2 \times 2+4 \times 4-3 \times 3+5 \times 5-4 \times 4+\cdots+20 \times 20-19 \times 19 \\
& =20 \times 20-2 \times 2 \\
& =400-4 \\
& =396
\end{aligned}
$$