75x+35≥7(11x+9)+475x+35≥7(11x+9)+4
75x+35≥77x+63+475x+35≥77x+63+4 [expand all blackets]
75x+35≥77x+6775x+35≥77x+67 [collect like terms]
−2x+35≥67−2x+35≥67 −2x≥32−2x≥32 [subtract 77x through]
x≤−16x≤−16
[subtract 35 through and divide through by 2]
If you notice the terms, they're
7, -21, 63, -189 and so forth.
7*-3 = -21 and -21 * -3 is 63 and so forth, meaning the "common ratio" is -3.
now, for a common ratio say "r", which is a fraction, namely less than ±1 and more than 0, or |r| < 1 , you do have a convergent sequence.
however this one notice, |-3| is 3, and that's greater than 1 clearly, therefore is divergent, meaning the summation has no finite value.
The length of a circumference: l=πD
l₁=π×5=5π
l₂=π×15=15π
Then l₂÷l₁=15π÷5π=3 and the answer is B)
