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3 years ago

Which of the following pairs of circles have/as a common external tangent select all that apply

Mathematics

1 answer:

iragen [17]3 years ago

3 0

Answer:

i need a picture cuz i dont see any external that apply

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Determine formula of the nth term 2, 6, 12 20 30,42

nalin [4]

Check the forward differences of the sequence.

If $\{a_n\} = \{2,6,12,20,30,42,\ldots\}$ , then let $\{b_n\}$ be the sequence of first-order differences of $\{a_n\}$ . That is, for n ≥ 1,

$b_n = a_{n+1} - a_n$

so that $\{b_n\} = \{4, 6, 8, 10, 12, \ldots\}$ .

Let $\{c_n\}$ be the sequence of differences of $\{b_n\}$ ,

$c_n = b_{n+1} - b_n$

and we see that this is a constant sequence, $\{c_n\} = \{2, 2, 2, 2, \ldots\}$ . In other words, $\{b_n\}$ is an arithmetic sequence with common difference between terms of 2. That is,

$2 = b_{n+1} - b_n \implies b_{n+1} = b_n + 2$

and we can solve for $b_n$ in terms of $b_1=4$ :

$b_{n+1} = b_n + 2$

$b_{n+1} = (b_{n-1}+2) + 2 = b_{n-1} + 2\times2$

$b_{n+1} = (b_{n-2}+2) + 2\times2 = b_{n-2} + 3\times2$

and so on down to

$b_{n+1} = b_1 + 2n \implies b_{n+1} = 2n + 4 \implies b_n = 2(n-1)+4 = 2(n + 1)$

We solve for $a_n$ in the same way.

$2(n+1) = a_{n+1} - a_n \implies a_{n+1} = a_n + 2(n + 1)$

Then

$a_{n+1} = (a_{n-1} + 2n) + 2(n+1) \\ ~~~~~~~= a_{n-1} + 2 ((n+1) + n)$

$a_{n+1} = (a_{n-2} + 2(n-1)) + 2((n+1)+n) \\ ~~~~~~~ = a_{n-2} + 2 ((n+1) + n + (n-1))$

$a_{n+1} = (a_{n-3} + 2(n-2)) + 2((n+1)+n+(n-1)) \\ ~~~~~~~= a_{n-3} + 2 ((n+1) + n + (n-1) + (n-2))$

and so on down to

$a_{n+1} = a_1 + 2 \displaystyle \sum_{k=2}^{n+1} k = 2 + 2 \times \frac{n(n+3)}2$

$\implies a_{n+1} = n^2 + 3n + 2 \implies \boxed{a_n = n^2 + n}$

6 0

2 years ago

#17-1: Simplify this complex fraction. 1/3 / 6/9

Gnesinka [82]

$\huge{\boxed{\frac{1}{2}}}$

To divide by a fraction, you multiply by its reciprocal, which you find by flipping the numerator and the denominator. $\frac{1}{3} \div \frac{6}{9} = \frac{1}{3} * \frac{9}{6}$

Multiply the numerators and the denominators separately. $\frac{1}{3} * \frac{9}{6} = \frac{1*9}{3*6} = \frac{9}{18}$

Simplify by dividing both sides of the equation by $9$ . $\frac{9 \div 9}{18 \div 9} = \boxed{\frac{1}{2}}$

3 0

3 years ago

Read 2 more answers

-2x < -6

Soloha48 [4]

Answer:

x > 3

Step-by-step explanation:

This is based on the concept 'when a negative number is multiplied to both sides of the inequality, the sign gets reversed. For example, x > - 2 when it is multiplied by - 1, it becomes - x < 2.'

*only when the number is -ve.

Similarly, in this question, multiply both sides by - 1.

2x > 6

x > 6/2

x > 3

For more : take - 5 > - 2, as you know

Note that 5 is actually greater than 2. To make this true we change signs

8 0

3 years ago

In the diagram AB is parallel to CD. Calculate the value of A ?

olga55 [171]

The image of the diagram is missing, so i have attached it.

Answer:

a = 30°

Step-by-step explanation:

From the diagram attached, we can see that the 2 angles a and 5a are interior supplementary angles.

The sum of interior supplementary angles is 180°

Thus;

5a + a = 180

6a = 180

a = 180/6

a = 30°

4 0

3 years ago

Solve absolute value equation [3x+5]-3

ehidna [41]

Its 2. because yea you know whats going on

7 0

3 years ago

Read 2 more answers