If y is the smallest positive integer such that 3150 mult by y is the square of an integer, then y must be:
A) 2
B) 5
C) 6
D) 7
E) 14
I understand that i will need to break down the prime factorization of 3150, but am stuck after that. don't know what to do...
thanks so much in advance.
Number Properties Problem Solving
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- thephoenix
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- sars72
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we need to find out the prime factors of 3150
-> 3150 = 315 * 10 = 63 * 5 * 2 * 5= 3 * 21 * 5 * 2 * 5 = 3*3*7*5*2*5 = 2 * 3^2 * 5^2 * 7
for this to be a perfect square, we need to make 2 and 7 power of 2, which can be done by multiplying the expressin by 2*7
-> 14
-> 3150 = 315 * 10 = 63 * 5 * 2 * 5= 3 * 21 * 5 * 2 * 5 = 3*3*7*5*2*5 = 2 * 3^2 * 5^2 * 7
for this to be a perfect square, we need to make 2 and 7 power of 2, which can be done by multiplying the expressin by 2*7
-> 14
- sars72
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the question asks us what number multiplied by 3150 will give us a square number i.e. a result of an integer raised to the power 2mstone wrote:so why can't i use the other prime factors? why only 2 and 7? thanks so much.
for this two happen, all the prime factors of 3150*y have to be raised to the power 2 or 4 or ....
since can be broken down to (2 * 3^2 * 5^2 * 7), we see that only 2 and 7 are not raised to the second power.
Since we have to find the smallest number ,y, which when multiplied with 3150 will give us a square of an integer, the answer is 2 * 7, which will give a square.
Hope this helped u understand why we use 2 and 7