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
Answer:
They will be picked up at 2 
yards above sea level
Step-by-step explanation:
Let us consider sea level as reference and positions above sea level as positive and below sea level as negative.
With respect to this reference,
the position of top most point is +17 
yards
and the position of lower most point is -13 yards
⇒ The position of midpoint is 
= +2
∴ <u>They will be picked up at 2 yards above sea level</u>
4 because if u where to fold it
Answer:
4/11
Step-by-step explanation:
1 blue, 2 green, 3 red, and 5 yellow marbles.= 11 marbles
P( blue or red) = number of blue or red / total
= 4/11
Answer:
Cups of carrot needed for 9 servings = 4.5 cups
Step-by-step explanation:
A recipe for sesame chicken calls for cup of chopped carrots
recipe 2 is for 4 servings
That is
2 cups of carrot = 4 servings
2 : 4
= 1 : 2
1 cup of carrot = 2 servings
how many cups of
carrots are needed for 9 servings?
Let x= number of carrot needed for 9 servings
1 : 2 = x : 9
1 /2 = x/ 9
Cross product
1*9 = 2*x
9=2x
Divide both sides by 2
9/2 = x
x= 4.5 Or 4 1/2
