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determine the 2nd and 3rd terms of a geometric sequence of which T1 =5 and T4=40​

Determine The 2nd And 3rd Terms Of A Geometric Sequence Of Which T1 5 And T440 class=

Sagot :

Answer:

Second term of this sequence: [tex]10[/tex].

Third term of this sequence: [tex]20[/tex].

Step-by-step explanation:

The first step is to find the common ratio of this sequence.

In a geometric sequence, multiply one term by the common ratio to find an expression for the next term. Let [tex]r[/tex] denote the common ratio of this sequence. For this sequence:

  • The first term of this sequence is [tex]5[/tex].
  • Multiply the first term by the common ratio to find an expression for the third term: [tex]5\, r[/tex].
  • Multiply the second term by the common ratio to find an expression for the fourth term: [tex]5\, r^{2}[/tex].
  • Similarly, an expression for the the fourth term would be: [tex]5\, r^{3}[/tex].

However, the question states that the value of the fourth term is [tex]40[/tex]. In other words, [tex]5\, r^{3} = 40[/tex].

Solve this equation for [tex]r[/tex]:

[tex]r^{3} = 8[/tex].

[tex]r = 2[/tex].

(Since the power of [tex]r[/tex] is non-even in the equation, there's no need to consider the sign of [tex]r\![/tex] when taking the cube root.)

Substitute [tex]r = 2[/tex] into the expression for the second term and the third term to find their values:

  • Second term: [tex]5\, r = 10[/tex].
  • Third term: [tex]5\, r^{2} = 20[/tex].