you just have to move the decimal point 9 places to the right thats an easy trick to remember 1849900000
6 - (-2) - 3(-5) = (6 + 2) + 15 = 8 + 15 = 23
Your answer is D. the last one :)
Your solution to your question would be 7a - 1967
800 different sets of digits
Since the first digit is a factor of 20, the factors of 20 are 1,2,4,5,10,20. We only need the single digit factors which are 1,2,4 and 5. These 4 numbers can be permuted in 1 way for the first digit, so we have ⁴P₁.
For the second digit, we have 10 digits permuted in 1 way, ¹⁰P₁ and also for the third digit, we have 10 digits permuted in 1 way, ¹⁰P₁ and for the last digit, which is divisible by 5, it is either a 0 or 5, so we have two digits permuted in 1 way, ²P₁.
So, the number of different 4 digit number that Zara'2 4-digit PIN code could be is ⁴P₁ × ¹⁰P₁ × ¹⁰P₁ × ²P₁ = 4 × 10 × 10 × 2 = 800 different sets of digits
Divide by greatest common factor.
Answer simplified should be 6y(4x^2-1)
Rewrite in the form where a^2-b^2
Answer
6y(2x+1)(2x-1)
