If LCM of two prime numbers a and b (a>b) is 783 , then the value of 2ab-3a is?

LCM(a, b) means the least common multiple between a and b.

LCM(a,b) = a*b/GCF(a,b)

Where GCF(a,b) =  greatest common factor between a and b.

Then the smallest common multiple between two prime numbers is the product between those prime numbers (Because the only common factor between prime numbers is 1).

LCM(a,b) = a*b = 783.

Now, to find the values of a and b, we can divide 783 by different primes, and see when the quotient is an integer:

(I ignore the number 2 because 783 is not even, so i will start with the prime 3)

783/3 = 261

Then the two primes are 3 and 261

We also know that a > b

Then:

a = 261

b = 3.

2*a*b - 3*a = 2*261*3 - 3*261 = 261*3*(2 - 1) = 261*3 = 783

you probably already have the answer but anyways it's b. 15.0

step-by-step explanation: