All GRE Subject Test: Math Resources
Example Questions
Example Question #131 : Linear Algebra
Solve this system of equations.
To solve this system of equations, subtract the second equation from the first.
____________________________
Now, substitute in the value for x into one of the equations to solve for the value of .
Now subtract five from each side.
Divide both sides by negative 2:
is the correct answer.
Example Question #14 : Solving Systems Of Equations
Solve this system of equations:
To solve this system of equations, set both equations equal to one another.
Add to both sides of the equation.
Subtract from both sides of the equation.
Multiply both sides of the equation by .
Plug the value of , which is into one of the equations to get the value of
is the correct answer for this system of equations.
Example Question #131 : Linear Algebra
Find the value of and that satisfy the equations:
(1)
and
(2).
Step 1: Write the two equations, one below another and line up the terms.
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Step 2: We see that we have and . We can add these two equations up, which will isolate y and let us solve for x.
We add here.
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Step 3: We will isolate x by itself. We need to divide by 2 on both sides to get x.
Step 4: We found x, so we can plug in that value into any one of the two equations and solve for y. Let's choose equation (1).
(1)...
. Isolate y by itself. We are going to subtract 6 from both sides.
. Simplify the left hand side.
Step 5: We will divide by -1 to get the value of y.
The values that solve this system of equations is and .
Example Question #302 : Algebra
Unsolvable
To answer this question you must first solve for one of the variables. This can be done with either variable with either equation. In this example of how to solve the problem we will solve for y using the second equation
subtract 8x from both sides
divide both sides by y
Now we plug this into the first equation for the y variable
Distribute the 3
Simplify
subtract 9 from both sides
divide by -2 on both sides
Using this we solve for y in the second equation
simplify
add 8 to both sides
divide by 4 on both sides
Final answer and
Example Question #1 : Eigenvalues
Find the eigenvalues of the following matrix, if possible.
The eigenvalues do not exist.
In order to find the eigenvalues of a matrix, apply the following formula:
is the identity matrix.
Compute the determinant and set it equal to zero.
Solve for lambda by using the quadratic formula.
Example Question #1 : Eigenspace Classifications
Find the eigenvalues of the following matrix, if possible.
The eigenvalues do not exist.
In order to find the eigenvalues of a matrix, apply the following formula:
is the identity matrix.
Compute the determinant and set it equal to zero.
Solve for lambda by using the quadratic formula.
Example Question #1 : Abstract Algebra
Let be the fifth-degree Taylor polynomial approximation for , centered at .
What is the Lagrange error of the polynomial approximation to ?
The fifth degree Taylor polynomial approximating centered at is:
The Lagrange error is the absolute value of the next term in the sequence, which is equal to .
We need only evaluate this at and thus we obtain
Example Question #2 : Abstract Algebra
Which of the following series does not converge?
We can show that the series diverges using the ratio test.
will dominate over since it's a higher order term. Clearly, L will not be less than, which is necessary for absolute convergence.
Alternatively, it's clear that is much greater than , and thus having in the numerator will make the series diverge by the limit test (since the terms clearly don't converge to zero).
The other series will converge by alternating series test, ratio test, geometric series, and comparison tests.
Example Question #1 : Applications Of Partial Derivatives
Find the minimum and maximum of , subject to the constraint .
is a maximum
is a minimum
is a maximum
is a minimum
There are no maximums or minimums
is a maximum
is a minimum
is a maximum
is a minimum
is a maximum
is a minimum
First we need to set up our system of equations.
Now lets plug in these constraints.
Now we solve for
If
,
If
,
Now lets plug in these values of , and into the original equation.
We can conclude from this that is a maximum, and is a minimum.
Example Question #1 : Lagrange Multipliers
Find the absolute minimum value of the function subject to the constraint .
Let To find the absolute minimum value, we must solve the system of equations given by
.
So this system of equations is
, , .
Taking partial derivatives and substituting as indicated, this becomes
.
From the left equation, we see either or . If , then substituting this into the other equations, we can solve for , and get , , giving two extreme candidate points at .
On the other hand, if instead , this forces from the 2nd equation, and from the 3rd equation. This gives us two more extreme candidate points; .
Taking all four of our found points, and plugging them back into , we have
.
Hence the absolute minimum value is .
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