Decades: 20s BC - 10s BC - 0s BC - 0s - 10s - 20s - 30s - 40s - 50s - 60s - 70s
Years: 20 21 22 23 24 25 26 27 28 29
Significant People
... 2, the element 2a is zero and it is impossible to divide by it.) The symbol <math>\pm \sqrt {b^2-4ac}</math> in the formula should be understood ...