Answer:
the common ratio is either 2 or -2.
the sum of the first 7 terms is then either 765 or 255
Step-by-step explanation:
a geometric sequence or series of progression (these are the most common names for the same thing) means that every new term of the sequence is created by multiplying the previous term by a constant factor which is called the common ratio.
so,
a1
a2 = a1×f
a3 = a2×f = a1×f²
a4 = a3×f = a1×f³
the problem description here tells us
a3 = 4×a1
and from above we know a3 = a1×f².
so, f² = 4
and therefore the common ratio = f = 2 or -2 (we need to keep that in mind).
again, the problem description tells us
a2 + a4 = 30
a1×f + a1×f³ = 30
for f = 2
a1×2 + a1×2³ = 30
2a1 + 8a1 = 30
10a1 = 30
a1 = 3
for f = -2
a1×-2 + a1×(-2)³ = 30
-10a1 = 30
a1 = -3
the sum of the first n terms of a geometric sequence is
sn = a1×(1 - f^(n+1))/(1-f) for f <>1
so, for f = 2
s7 = 3×(1 - 2⁸)/(1-2) = 3×-255/-1 = 3×255 = 765
for f = -2
s7 = -3×(1 - (-2)⁸)/(1 - -2) = -3×(1-256)/3 = -3×-255/3 =
= -1×-255 = 255
Great question! I had this question in Geometry on Edmentum.
Answer: Height of cone = 3y
Step-by-step explanation:
We know that the cylinder and the cone have the same volume. The cylinder has radius x and height y. We will make use of the formulas:
Volume of cylinder = πr²h
Volume of cone = 1/3πr²h
Since the cone has radius 1/3x, we will have to make its height 3 times of y (the height of the cylinder) to make both the cylinder and the cone have the same volume.
So, the height of the cone is equal to 3y.
Hope this helps, and have a wonderful day! :D
Please mark me brainliest! I don't have trouble getting points, but I do when it comes to brainliest.
Answer:
Cos E= 24/25
Step-by-step explanation:
Length of hypotenuse: 7^2+24^2=625. 625 square root=25
Thus, DE is 25.
Sin D= 24/25, so that is false.
Tan D= 24/7, so that is false.
Cos E= 24/25, so that is true
Sin E= 7/25, so that is false.
Answer:
B
Step-by-step explanation:
None of the numbers repeat unlike the other decimals
Answer:
Step-by-step explanation:
Subtract 2 from both sides:
Subtract 5x from both sides:
Divide both sides by 2:
