If a + b + c = 6, a³ + b³+c³-3abc=342, then what is the value of ab + bc + ca?

and x is real, then the value of is

if 2x² – 7x + 5 =0, then what is the value of

If x = 19 and y = 18, then the value of   is

If 27(x+y)³ – 8(x-y)³=(x+5y)(Ax²+By²+Cxy), then what is the value of (A+B-C)?

If    then the value of a³ + b³ is 

If a + b – c = 0 then the value of 2b²c² + 2c²a² + 2a²b² –a⁴ – b⁴ – c⁴

If , , and are three distinct prime numbers, then what is the least common multiple of , , and ?