上三角：

[sq4250]

[sq4250]

#include<stdio.h>
int main(){
    for(int a=1;a<10;a++){
        int i=a;
        for(int b=1;b<a;b++)printf("       ");
        while(i<10){
            printf("%d*%d=%2d ",a,i,a*i);
            i++;
        }
        printf("\n");
    }
    return 0;
}

[sq4250]

#include<stdio.h>
int main(){
    for(int a=1;a<10;a++){
        for(int b=1;b<a;b++)printf("       ");
        for(int i=a;i<10;i++)printf("%d*%d=%2d ",a,i,a*i);
        printf("\n");
    }
    return 0;
}

[sq4250]

$$ det\begin{bmatrix}a-x&b&c\\1&-x&0\\0&1&-x\end{bmatrix}=\left(a-x\right)\begin{vmatrix}-x&0\\1&-x\end{vmatrix}+\left(-1\right)\begin{vmatrix}b&c\\1&-x\end{vmatrix}=\left(a-x\right)x^{2}-\left(-bx-c\right)=ax^{2}-x^{3}+bx+c $$