This is a geometric sequence with common ratio (r) = 2.
an = ar^(n - 1)
a4 = a(2)^(4 - 1) = a(2)^3 = 8a
8a = 80
a = 80/8 = 10
7th term (a7) = 10(2)^(7 - 1) = 10(2^6) = 10(64) = 640
Answer:
y = 0.5x
Step-by-step explanation:
The equation of a line in slope- intercept form is
y = mx + c ( m is the slope and c the y- intercept )
y = 0.5x - 2 ← is in slope- intercept form
with slope m = 0.5
Parallel lines have equal slopes, thus
y = 0.5x + c ← is the partial equation
To find c substitute (- 2, 1) into the partial equation
- 1 = - 1 + c ⇒ - 1 + 1 = 0
y = 0.5x + 0 , that is
y = 0.5x ← equation of parallel line
Solve for x:
x^9 = n x
Subtract n x from both sides:
x^9 - n x = 0
Factor x and constant terms from the left hand side:
-x (n - x^8) = 0
Multiply both sides by -1:
x (n - x^8) = 0
Split into two equations:
x = 0 or n - x^8 = 0
Subtract n from both sides:
x = 0 or -x^8 = -n
Multiply both sides by -1:
x = 0 or x^8 = n
Taking 8^th roots gives n^(1/8) times the 8^th roots of unity:
Answer: x = 0 or x = -n^(1/8) or x = -i n^(1/8) or x = i n^(1/8) or x = n^(1/8) or x = -(-1)^(1/4) n^(1/8) or x = (-1)^(1/4) n^(1/8) or x = -(-1)^(3/4) n^(1/8) or x = (-1)^(3/4) n^(1/8)
