If A B = 8 2 , is it true that A × B must equal 16?
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Can we write unreal,irrational & rational solutions?
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Yes, of course. Just for real A B = 8 2 ⟹ B ln A = 6 ln 2 ⟹ ln A = B 6 ln 2 . Implying for B ∈ ( 0 , ∞ ) , A ∈ ( − ∞ , ∞ ) . There are infinitely many solutions. If B < 0 , there will be complex solutions for A .
the question wasn't clear!
Or it could just be 64¼½ which is 8. 8 squared is 64, but 8 × 2 is 16 - which is AB, which must either be 4 squared or 8 x 2.
8^2=8^2 so then A^B=8^2 A×B=8×2=16
This is questionable. A^B=8^2=2^6= B^C this is what I read... there’s not written A^B=64
Does it mean to say that this question has finite solution.
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Infinite many solutions. Just for real solutions A B = 8 2 ⟹ B ln A = 6 ln 2 ⟹ ln A = B 6 ln 2 . Implying for B ∈ ( 0 , ∞ ) , A ∈ ( − ∞ , ∞ ) . There are infinitely many solutions. If B < 0 , there will be complex solutions for A .
Eh, you assign 8 to A and 2 to B right? I was always told that variables in math are immutable, so how can A become 2 and B become 6 then?
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A B = 8 2 = ( 2 3 ) 2 = 2 6 . I don't understand the immutable bit.
Integer solutions include ( A , B ) = ( 8 , 2 ) , ( 4 , 3 ) , ( 2 , 6 ) , ( 1 , 6 4 ) , giving A × B = 1 6 , 1 2 , 1 2 , 6 4 . However there are many more solutions if one considers that A and B don't necessarily have to be integers: A B ln A B B ln A B A × B f ( A ) = A × B When A = 3 , When A = 1 3 , By the intermediate value theorem, = 6 4 = ln 6 4 = ln 6 4 = ln A ln 6 4 = ln A A ln 6 4 is a continuous function for A > 1 A × B ≈ 1 1 . 3 5 6 7 A × B ≈ 2 1 . 0 7 8 6 (just any larger number will do for this proof.) there exists real values of A such that A × B = 1 2 , 1 3 , 1 4 , etc.
What about 64^1?
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The problem has changed since I posted this solution, and originally asked for whether 12, 16 or 20 are possible, to which the answer is all of them. Getting 20 as an answer requires A and B to be irrational, which I suppose is now the key point in this solution. I have edited the solution to reflect this.
Great proof
A B = 6 4 1 = 8 2 ( o r ) ( − 8 ) 2 = 2 6 ( o r ) ( − 2 ) 6 = 4 3
So, the possible values of A × B are : 6 4 × 1 = 6 4 8 × 2 = 1 6 ( o r ) − 8 × 2 = − 1 6 2 × 6 = 1 2 ( o r ) − 2 × 6 = − 1 2 4 × 3 = 1 2
Since we now have very similar solutions, I deleted my solution and upvoted yours.
A and B are not necessarily integers...
The red graph is ( A , B ) such that A B = 6 4 . Although the point ( 8 , 2 ) can be seen, there are plenty of other points.
A B = 6 4 means B = ln A ln 6 4 . So A × B = A ln A ln 6 4 . This is the black graph.
Again, directly above ( 8 , 2 ) is ( 8 , 1 6 ) but the black graph reaches plenty of other heights.
In fact every height e ln 6 4 or above and below 0 is in the range.
This is all I needed to do for this question, too. No need to dive further unless there was a bonus question for a more general case
Or (the fifth root of 64)^5, since 64 is not a perfect 5th
well... 4 0 9 6 2 1 works, and product of A and B is 2048.
A = 2 2 i and B = 4 . There was no statement that A and B must be real numbers.
The question being asked is must be true, what you have shown here is that it may be true.
Since A B = 8 2 = 6 4 we have:
B = l o g A 6 4
And, therefore:
A B = A ⋅ l o g A 6 4 = l o g A 6 4 A
The latter relation being independent of the value of A , and thus valid for each real value of A and B . We could, for example, give to A and B the values:
A = e
B = l n 6 4 ≈ 4 . 1 5 9
Or trivially:
A = 6 4
B = 1
In both cases, A ⋅ B = 1 6 , being approximately 1 1 . 3 0 5 if A = e and 6 4 if A = 6 4 .
what we know: A^B = 8^2 = 64
what we want to know: Does AxB always = 16?
64^1 also equals 64 so no
No. For instance: 2^6 = 8^2 so A x B could also be 12 (4^3 is another one)
The answer is "No" because (-8)^2 = 8^2 so A may equals -8 or 8. If A equals -8, A*B = -16.
The awnser must be NO , since: (b)^a =(-b)^a BUT b x a Does not equal -b x a
In this case, 8^2 is equal to (-8)^2, both equal to 64, but the first expression is equal to 64 while the latter is -64
We could provide the easy counterexample:
A B = 8 2 ⇔ A = B 1 6
For example B : = 3 , then:
A = 3 1 6
and obviously
A B = 3 1 6 ⋅ 3 = 1 6
Because 6 4 can write in form of A B = 2 6 = 4 3 = 8 2 = 6 4 1 = … which the answer(s) is ⎩ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎨ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎧ 8 × 2 = 1 6 2 × 6 = 1 2 4 × 3 = 1 2 6 4 × 1 = 6 4 = … so the answer is N o
For the sake of putting π in every solution : A = 6 4 π 1 and B = π which gives us A × B = 6 4 π 1 × π (Irrationnal number)
6 4 1 = 8 2
6 4 × 1 = 1 6
Since 2^6=64 2*6=12 12 does not equal 16.
(-8)^2 = 8^2 and gives as A x B.......-16
8^2=(2^3)^2 =2^6 So A=2 , B=6 here which equals 12 not 16 so it's not true
A B = 8 2 = 6 4 ⟹ B = lo g A 6 4
A × B = A lo g A 6 4 . Plug in almost any value for A and the result will not be 1 6 . For example, A = 2 yields A × B = 1 2 . Also, if 0 < A < 1 , the answer will always be negative and therefore will never be 1 6 .
Since A B = 8 2 = 4 3 = 2 6
The possible value of A B is 1 6 , 1 2 . This is enough to raise a contradiction, hence no.
This question should state that A and B are Integers so that it is more challenging.
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The answer is " No " because digital solutions alone we have three distinct solutions: A B = 8 2 = 2 6 = 4 3 = 6 4 1 ⟹ A × B = ⎩ ⎪ ⎪ ⎪ ⎨ ⎪ ⎪ ⎪ ⎧ 8 × 2 = 1 6 2 × 6 = 1 2 4 × 3 = 1 2 6 4 × 1 = 6 4