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What is the smallest positive integer n such that the fourth root of 98n is an integer?

 Jul 1, 2022
 #1
avatar+2668 
0

The prime factorization of 98 is 72×2

 

Because we are taking the fourth root, everything must be raised to a power of a multiple of 4, (4, 8, 12, etc.)

 

This means that the smallest value of n that works is 72×23=392 

 Jul 1, 2022
edited by BuilderBoi  Jul 1, 2022
 #2
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Thanks but im still confused how you got 7^2 and 2^3  

 Jul 1, 2022
 #3
avatar+2668 
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Thanks for the feedback!!

 

Note that because all the bases in the term 74×24 are raised to the 4th power, the 4th root of this is an integer. 

 

So, we basically have: 74×247x×2y=72×21

 

Start with 747x . We want this to equal 72

 

Recall that when you are dividing exponents with the same base, you subtract the exponents (34÷32=342=32).

 

Applying that here, we have 74÷7x=72, thus x=2. (74÷72=742=72)

 

Now, doing the same thing to 242y. We want this to equal 21, so y=3. (24÷23=243=21).

 

So, the answer we are looking for is 72×23=392

 

Hope this helps!

 Jul 1, 2022
 #4
avatar+1166 
+10

 

The smallest n ==392, because:

 

98 * 392 ==38,416^(1/4) ==14

 Jul 4, 2022
 #5
avatar+1166 
+10

you can also think about it this way

 

98 = 2*7*7
k=(2^4 x 7^4)/2x7x7

k=2^3 x 7^2 = 392

nerdiest  Jul 4, 2022

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