Answer:
96
Step-by-step explanation:
commom difference = d
a₆ + a₇ = 16
a₅ + a₈ = (a₆ - d) + (a₇ + d) = a₆ + a₇ = 16
a₄ + a₉ = (a₆ - 2d) + (a₇ + 2d) = a₆ + a₇ = 16
Similarly,
a₃ + a₁₀ = 16, a₂ + a₁₁ = 16, a₁ + a₁₂ = 16
so
a₁ + a₂ + ... + a₁₁ + a₁₂ = 6 x 16 = 96
Here you go. Hope you understand all of the work.
Answer:
x = 25
Step-by-step explanation:
.20x + .68(120 - x) = .54(120) (Distribute .68 to 120 and -x)
.20x + 81.6 - .68x = .54(120) (multiply .54 and 120)
.20x + 81.6 - .68x = 69.6 ( add .20x and -.68x)
-.48x + 81.6 = 69.6 ( subtract 81.6 on each side)
-.48x = -12 (divide -12 by -.48)
x = 25
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a = a + d(n-1)
n 1
this is the formula for the arithmetic sequence.
the first sequence is arithmetic
an=1+7(n-1)
the second sequence is also arithmetic
an=12+4(n-1)
