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AveGali [126]
3 years ago
11

An Ap is such that 5 th term is three times the 2nd term.given further that the sum of the 5th,6th,7th,8th term is240,calculate

the value of the first term.​
Mathematics
1 answer:
Fiesta28 [93]3 years ago
8 0

Answer:

  5

Step-by-step explanation:

The general term of an arithmetic progression is ...

  an = a1 +d(n -1)

where a1 is the first term and d is the common difference.

Here we are given that ...

  a5 = 3×a2

  a5 +a6 +a7 +a8 = 240

__

In terms of a1 and d, these tell us ...

  a1 +d(5 -1) = 3(a1 +d(2 -1))

  a1 +4d = 3a1 +3d . . . . . eliminate parentheses

  d = 2a1 . . . . . . . . . . . subtract a1+3d

and ...

  (a1 +4d) +(a1 +5d) +(a1 +6d) +(a1 +7d) = 240

  4a1 +22d = 240

Substituting for d, we have ...

  4a1 +22(2a1) = 240

  48a1 = 240

  a1 = 240/48 = 5

The first term is 5.

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<h2>Hello!</h2>

The answer is: g(x)=-\sqrt[3]{x-1}

<h2>Why?</h2>

Let's check the roots and the shown point in the graphic (2,-1)

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0=-\sqrt[3]{x-1}\\\\0^{3}=(-\sqrt[3]{x-1})^{3}\\\\0=-(x-1)\\\\x=1

then,

g(0)=-\sqrt[3]{0-1}\\g(0)=-(-1)\\g(0)=1\\y=1

So,  we know that the function intercepts the axis at (1,0) and (0,1), meaning that the function match with the last given option

(g(x)=-\sqrt[3]{x-1})

Second,

Evaluating the function at (2,-1)

y=-\sqrt[3]{x-1}\\-1=-\sqrt[3]{2-1}\\-1=-\sqrt[3]{1}\\-1=-(1)\\-1=-1

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It means that the function passes through the given point.

Hence,

The equation which represents g(x) is g(x)=-\sqrt[3]{x-1}

Have a nice day!

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