A student needs at least seven hours of sleep each night the student goes to bed at 11 pm and wakes up before 6:30 am is the stu
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We want to find the values of a, b, c, and d such that the given matrix product is equal to a 2x2 identity matrix. We will solve a system of equations to find:
- b = 1
- a = -1
- c = -2
- d = -1
<h3>Presenting the equation:</h3>
Basically, we want to solve:
The matrix product will be:
Then we must have:
-b + 2 = 1
This means that:
b = 2 - 1 = 1
- b = 1
We also need to have:
a*b + 1 = 0
we know the value of b, so we just have:
a*1 + b = 0
- a = -1
Now the two remaining equations are:
-c + 2d = 0
a*c + d = 1
Replacing the value of a we get:
-c + 2d = 0
-c + d = 1
Isolating c in the first equation we get:
c = 2d
Replacing that in the other equation we get:
-(2d) + d = 1
-d = 1
- d = -1
Then:
c = 2d = 2*(-1) = -2
- c = -2
So the values are:
- b = 1
- a = -1
- c = -2
- d = -1
If you want to learn more about systems of equations, you can read:
Let's call the distance from the beach to the playground x.
Let's call the distance from the stand to the parking lot z.
Let's call the base of the biggest triangle in the picture (from the parking lot to the left) y.
Recall the pythagorean theorem: the sum of the squares of the legs of a right triangle is equal to the square of the hypotenuse.
There are three right triangles we can work with.
Triangle with sides 48, x and z. Here z is the hypotenuse so we get the equation
Triangle with sides 27, x and y. Here y is the hypotenuse so we get
Triangle with sides z, y and (48+27). Here (48+27) is the hypotenuse so we get
. That is, 
We have 3 equations and 3 unknowns (x, y and z). So let's take the last equation:
and replace 
and 
using expressions that contain an expression in terms of x from the first two equations we came up with.
That gives us:
which we solve for x as follows:
Now that we know x we can substitute 36 for x into the equation
and solve for z as follows:
This means that the distance from the beach to the parking lot is 36 m and the distance from the stand to the parking lot is 60 m.
Let's call the distance from the stand to the parking lot z.
Let's call the base of the biggest triangle in the picture (from the parking lot to the left) y.
Recall the pythagorean theorem: the sum of the squares of the legs of a right triangle is equal to the square of the hypotenuse.
There are three right triangles we can work with.
Triangle with sides 48, x and z. Here z is the hypotenuse so we get the equation
Triangle with sides 27, x and y. Here y is the hypotenuse so we get
Triangle with sides z, y and (48+27). Here (48+27) is the hypotenuse so we get
We have 3 equations and 3 unknowns (x, y and z). So let's take the last equation:
That gives us:
Now that we know x we can substitute 36 for x into the equation
This means that the distance from the beach to the parking lot is 36 m and the distance from the stand to the parking lot is 60 m.