Discover Questions

If a number is divisible by 5 how do you know it will be divisible by 15? How do you solve this math problem? Please needed Immediately Rational Root Theorem
4x^4-65x^2+60? ABCD is a square and BX = BY prove that 1) DCX congruent to DAY 2) DY = DX
3) How does the double cross magic pen by Mark southworth work? Thanks.? 3 x 4 ÷ 6 x 2... what's is the answer?