Why is the quadratic expression 20*x^2-1 only divisible by decimal numbers ending in -1 , or ending in -9 ?(adsbygoogle = window.adsbygoogle || []).push({});

Sorry! My profile is a semi-retired carer.Location London(South) . Male 59. Have rudimentary maths -interests Number Theory , Prime Numbers.

**Physics Forums - The Fusion of Science and Community**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Quadratic expression integer iterations

**Physics Forums - The Fusion of Science and Community**