Answer:
Step-by-step explanation:
In order to solve this problem we must start by graphing the given function and finding the differential area we will use to set our integral up. (See attached picture).
The formula we will use for this problem is the following:
where:
a=0
so the volume becomes:
This can be simplified to:
and the integral can be rewritten like this:
which is a standard integral so we solve it to:
so we get:
which yields:
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Answers:
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Explanation:
Problem 1
This is false because the A and B should swap places. It should be .
The short proof is to multiply AB with its inverse and we get:
The fact we get the identity matrix proves that we have the proper order at this point. The swap happens so that B matches up its corresponding inverse and the two cancel each other out.
Keep in mind matrix multiplication is <u>not</u> commutative. So AB is not the same as BA.
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Problem 2
This statement is true if and only if AB = BA
(A+B)^2 = (A+B)(A+B)
(A+B)^2 = A(A+B) + B(A+B)
(A+B)^2 = A^2 + AB + BA + B^2
(A+B)^2 = A^2 + 2AB + B^2 ... only works if AB = BA
However, in most general settings, matrix multiplication is <u>not</u> commutative. The order is important when multiplying most two matrices. Only for special circumstances is when AB = BA going to happen. In general, AB = BA is false which is why statement two breaks down and is false in general.
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Problem 3
This statement is true.
If A and B are invertible, then so is AB.
This is because both and
are known to exist (otherwise A and B wouldn't be invertible) and we can use the rule mentioned in problem 1. Make sure to swap the terms of course.
Or you can use a determinant argument to prove the claim
det(A*B) = det(A)*det(B)
Since A and B are invertible, their determinants det(A) and det(B) are nonzero which makes the right hand side nonzero. Therefore det(A*B) is nonzero and AB has an inverse.
So if we have two invertible matrices, then their product is also invertible. This idea can be scaled up to include things like A^4*B^3 being also invertible.
If you wanted, you can carefully go through it like this:
and so on until you build up to A^4*B^3. Therefore, we can conclude that A^m*B^n is also invertible. Be careful about the order of multiplying the matrices. Something like A*AB is different from AB*A, the first of which is useful while the second is not.
So this is why statement 3 is true.
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Problem 4
This is false. Possibly a quick counter-example is to consider these two matrices
both of which are invertible since their determinant is nonzero (recall the determinant of a diagonal matrix is simply the product along the diagonal entries). So it's not too hard to show that the determinant of each is 1, and each matrix shown is invertible.
However, adding those two mentioned matrices gets us the 2x2 zero matrix, which is a matrix of nothing but zeros. Clearly the zero matrix has determinant zero and is therefore not invertible.
There are some cases when A+B may be invertible, but it's not true in general.
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Problem 5
This is true because each A pairs up with an to cancel out (similar what happened with problem 1). For more info, check out the concept of diagonalization.
Answer:
63 Jelly Beans
Step-by-step explanation:
The unknown is the number of jelly beans originally in the bag or x
First he had x jelly beans
The he ate one-third of them
He then ate 16 more jelly beans
This was equal to 37 jelly beans
This is the equation
Now solve for x
Subtract 16 from both sides
Multiply both sides by 3
63 Jelly Beans