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Annette [7]
3 years ago
9

In Exercises 23–36, solve the system using either Gaussian elimina- tion with back-substitution or Gauss-Jordan elimination. 23.

x + 2y = 7 2x + y = 8 25. - x + 2y = 1.5 2x – 4y = 3
Mathematics
1 answer:
Luba_88 [7]3 years ago
5 0

Answer:

23) x= 3, y = 4

24) Any (x,y) values where x = 1.5 - 2y

Step-by-step explanation:

For the first system(23), it goes like this

[1 2 | 7]

[2 1 | 8]

We need to do L2 = L2 - 2L1, so now it is

[1 2   | 7]

[0 -3 |-6]

So, now we have:

-3y = -6 *(-1)

3y = 6

y = 2

x + 2y = 7

x + 4 = 7

x = 3

Now for system 24, we have:

[-1 2 | 1.5]

[2 -4| 3]

We do L2 = L2 + 2L1, so we have:

[-1 2 | 1.5]

[0 0| 0]

So there are infinite solutions for this system. The solution for this system will be each (x,y) pair where x = 1.5 - 2y.

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lilavasa [31]

For this case we must factor the following expression:

d ^ 4-81

Rewriting the expression:

(d ^ 2) ^ 2-9 ^ 2

We factor using the formula of the square difference:

a ^ 2-b ^ 2 = (a + b) (a-b)

Where:

a = d ^ 2\\b = 9

So:

(d ^ 2 + 9) (d ^ 2-9)

From the second term we have:

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Finally, the factored expression is:

(d ^ 2 + 9) (d-3) (d + 3)

Answer:

(d ^ 2 + 9) (d-3) (d + 3)

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t=twent dollar bills

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