Exercise ID383

Algebra → Progressions → Arithmetic progressions
[Level: ] [Number of helps: 1] [Number of pictures: 0] [Number of steps: 11] [Number of characters: 145]

The fourth member of the arithmetic series is 7, and the fifth is -5.
Determine the first member of the series!

a4=7, a5=-5 (1) a4=a1+3d=7 (2) a5=a1+4d=-5 (1) a1+3d=7 (2) a1+4d=-5 (2)-(1) a1+4d-a1+3d=-5-7 (2)-(1) a1+4d-a1-3d=-5-7 d=-12 (1) a1=7-3d a1=7-3(-12)=7+36 a1=43
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a1=43
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