Answer:

Step-by-step explanation:
The given series is

The first term is

The last term is

To find the number of terms in the sequence, solve,


The sum of the first i-terms of an arithmetic sequence is:

We substitute the values to get;



Answer:
2. (1.5, 1.5)
Step-by-step explanation:
midpoint = (x1+x2)/2 , (y1+y2)/2
A = (-3,-3) and B = (6,6)
midpoint = (-3+6)/2, (-3+6)/2
= 3/2 , 3/2
Answer:
The required equation is
.
Step-by-step explanation:
If a quadratic equation is
, then the quadratic formula is

The given quadratic equation is

Here, a=1, b=-9 and c=-20.
Substitute a=1, b=-9 and c=-20 in the above quadratic formula.

Therefore the required equation is
.
Answer: ∠DOB: 48°
Step-by-step explanation:
1. we need an equation first. the sum of all angles (108°, n°, 2n°) is equal to 180°. we can depict this with the equation: 108°+2n°+n°=180°
2. now we can solve for the missing variable, n.
108°+3n°=180° → subtract both sides by → 3n°=72° → divide both sides by 3 → n=24°
3. now that we know that n=24°, we can solve the value of ∠DOB. we can see that ∠DOB is 2n° which we just plug the number we got for n into the equation. 2*24=48° meaning ∠DOB is 48°
hope this heped! ♡
The nth term of any geometric sequence can be expressed as:
a(n)=ar^(n-1), a(n)=nth term, a=initial term, r=common ratio, n=term number...
We can easily see that the first term, a=-8
The common ratio is 4/-8=-2/4=1/-2=r=-1/2 so the rule is:
a(n)=-8(-1/2)^(n-1) so the tenth term is:
a(10)=-8(-1/2)^(10-1)
a(10)=-8(-1/2)^9
a(10)=1/64