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dedylja [7]
3 years ago
11

-7x - 8y = 9 4x -9y = 22

Mathematics
1 answer:
umka21 [38]3 years ago
8 0

Answer:

x=1 and y=−2

Step-by-step explanation:

Multiply the first equation by 9,and multiply the second equation by -8.

9(−7x−8y=9)

−8(4x−9y=22)

Becomes:

−63x−72y=81

−32x+72y=−176

Add these equations to eliminate y:

−95x=−95

Then solve−95x=−95for x:

−95x

−95

=

−95

−95

(Divide both sides by -95)

x=1

Now that we've found x let's plug it back in to solve for y.

Write down an original equation:

−7x−8y=9

Substitute1forxin−7x−8y=9:

(−7)(1)−8y=9

−8y−7=9(Simplify both sides of the equation)

−8y−7+7=9+7(Add 7 to both sides)

−8y=16

−8y

−8

=

16

−8

(Divide both sides by -8)

y=−2

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3 years ago
the first term of an arithmetic sequence is 2 and the sum of the first 15 terms is 292.5. Find the common difference
adelina 88 [10]

Given:

First term of an arithmetic sequence is 2.

Sum of first 15 terms = 292.5

To find:

The common difference.

Solution:

We have,

First term: a=2

Sum of first 15 terms: S_{15}=292.5

The formula of sum of first n terms of an AP is

S_n=\dfrac{n}{2}[2a+(n-1)d]

Where, a is first term and d is common difference.

Putting S_{15}=292.5, n=15 and a=2 in the above formula, we get

292.5=\dfrac{15}{2}[2(2)+(15-1)d]

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292.5=15[2+7d]

Divide both sides by 15.

\dfrac{292.5}{15}=2+7d

19.5=2+7d

19.5-2=7d

17.5=7d

Dividing both sides by 7, we get

\dfrac{17.5}{7}=d

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Therefore, the common difference is 2.5.

8 0
3 years ago
Joe makes belts. He has 9 buckles. He uses 12 rivets on each of 4 belts and 15 rivets on each of 2 belts. He has 22 rivets left
Lerok [7]

Answers:

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2. Extra information given in the problem:

a. He has 9 buckles.

b. He has 22 rivets left over.


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Total rivets on the belts=78 rivets


2. The extra information given in the problem is the information that we didn't use to solve it. In this case:

a. He has 9 buckles.

b. He has 22 rivets left over.

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3 years ago
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Arada [10]

Answer:

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Step-by-step explanation:

4x4=16

16x6=96

5 0
3 years ago
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