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4 years ago

Find the sum of the first 20 terms of an arithmetic series if the first term is 10 and the twentieth term is 38.

Mathematics

1 answer:

elena-14-01-66 [18.8K]4 years ago

6 0

Answer:480

Step-by-step explanation:

To find the sum of the first n terms of an arithmetic series use the formula, n terms of an arithmetic sequence use the formula,

Sn=n(a1 + an)2

n=20

a1= 10

a20=38

20(10+38)/2

20(48)/2

960/2

480

So the ans is 480

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I don’t know the answer I need help

Elenna [48]

Answer:

$-11b^2+8b-4$

Step-by-step explanation:

We can substitute in our expressions for P and Q to get

$P=-4b^2+6b-9\\Q=7b^2-2b-5\\\\(-4b^2+6b-9)-(7b^2-2b-5)$

Next, we need to distribute the negative to the values within the parenthesis. Then we can combine like terms in order to get our answer

$(-4b^2+6b-9)-(7b^2-2b-5)\\\\-4b^2+6b-9-7b^2+2b+5\\\\-11b^2+8b-4$

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3 years ago

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Natalka [10]

2x + y = 3
x = 2y - 1

solve for y in the first equation;
2x + y = 3
y = 3 - 2x

x = 2y - 1
x = 2(3 - 2x) - 1
x = -4x + 5

solve for x;
x = -4x + 5
x + 4x = 5
5x = 5
x = 1

solve for y;
y = 3 - 2x
y = 3 - 2(1)
y = 1

the answer is: x = 1, y = 1

hope this helps, God bless!

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3 years ago

Ye has his own business. He checks his sales receipts three times a day, his afternoon sales were 50$ more than his mourning sal

IRINA_888 [86]

Answer:

The answer is 150

Step-by-step explanation:

It's 150 because ye evening sales are three times of his afternoon sales.

SO that means you have to times 50x3=150 or you can add 50+50+50=150. there is your answer.

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3 years ago

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The sum of x and it’s opposite is always zero?

jeka94

Answer:

1) Let's consider the first case with the number 0 the oppose is also 0 and we have that 0-0=0 so then applies

2) Now let's consider any real number a no matter positive or negative we will have that:

$a-a =0$

Or in the other case:

$-a -(-a) =-a +a=0$

So then we can conclude that the expression is a general rule and is true

Step-by-step explanation:

For this case we can verify if the following expression is true or false:

The sum of x and it’s opposite is always zero?

If we want to proof this we need to show that for any number is true.

1) Let's consider the first case with the number 0 the oppose is also 0 and we have that 0-0=0 so then applies

2) Now let's consider any real number a no matter positive or negative we will have that:

$a-a =0$

Or in the other case:

$-a -(-a) =-a +a=0$

So then we can conclude that the expression is a general rule and is true

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