Formula of parabola: x? =ky, and y? =kx, where k can be positive or negative.

Circular Decimal-Decimal Infinite Decimal, starting with the number after the decimal point and repeating the previous number or part.

Pure circulating decimal-the decimal that circulates from the tenth place, and enter 0.50000.00000000005

Mixed recurring decimal-the recurring part is not the recurring decimal starting from the first position of the decimal part, and it goes to 2.50000.00000000505

Light speed: 3x10 8m/s/s.

Sonic speed: about 340m/s at standard atmospheric pressure.