which sequences are arithmetic? select three options.\n-8.6, -5.0, -1.4, 2.2, 5.8, ...\n2, -2.2, 2.42…

Explanation:

Step1: Check the first sequence

For the sequence (-8.6,-5.0,-1.4,2.2,5.8,\cdots) Calculate the differences: (-5.0-\left(-8.6\right)=-5.0 + 8.6=3.6) (-1.4-\left(-5.0\right)=-1.4 + 5.0 = 3.6) (2.2-\left(-1.4\right)=2.2+1.4 = 3.6) (5.8 - 2.2=3.6) Since the common difference (d = 3.6), it is an arithmetic sequence.

Step2: Check the second sequence

For the sequence (2,-2.2,2.42,-2.662,2.9282,\cdots) Calculate the differences: (-2.2-2=-4.2) (2.42-\left(-2.2\right)=2.42 + 2.2=4.62) Since (-4.2\neq4.62), it is not an arithmetic sequence.

Step3: Check the third sequence

For the sequence (5,1,-3,-7,-11,\cdots) Calculate the differences: (1 - 5=-4) (-3-1=-4) (-7-\left(-3\right)=-7 + 3=-4) (-11-\left(-7\right)=-11 + 7=-4) Since the common difference (d=-4), it is an arithmetic sequence.

Step4: Check the fourth sequence

For the sequence (-3,3,9,15,21,\cdots) Calculate the differences: (3-\left(-3\right)=3 + 3=6) (9 - 3=6) (15-9=6) (21 - 15=6) Since the common difference (d = 6), it is an arithmetic sequence.

Step5: Check the fifth sequence

For the sequence (-6.2,-3.1,-1.55,-0.775,-0.3875,\cdots) Calculate the differences: (-3.1-\left(-6.2\right)=-3.1+6.2 = 3.1) (-1.55-\left(-3.1\right)=-1.55 + 3.1=1.55) Since (3.1\neq1.55), it is not an arithmetic sequence.

Answer:

(-8.6,-5.0,-1.4,2.2,5.8,\cdots), (5,1,-3,-7,-11,\cdots), (-3,3,9,15,21,\cdots)