Get Help And Discuss STEM Concepts From Math To Data Science & Financial Literacy
STEM Gender Equality | Join us on ZOOM | Spreading Mathematical Happiness

MathsGee is free of annoying ads. We want to keep it like this. You can help with your DONATION

0 like 0 dislike
137 views

The sequence $4 ; x ; y ; 18$ is such that $ 4 ; x ; y $ form an arithmetic sequence and $x,y$ and 18 form a geometric sequence

  1. Using the common difference of the arithmetic sequence, determine $y$ in terms of $x$
  2. Using the common ratio of the geometric sequence, determine $y$ in terms of $x$
  3. Hence, or otherwise, calculate the value(s) of $x$ and $y$

 

in Grade 12 Maths by Diamond (50,454 points) | 137 views

1 Answer

0 like 0 dislike
1. x-4=y-x

     y=2x-4

2. y/x = 18/y

       y^2 = 18x

          y= sqroot(18x)

3. y=2x-4

sqroot(18x)=2x-4

          18x= (2x-4)^2

         4x^2 -34x+16=0

      2x^2 -17x+8=0

   (2x-1)(x-8)=0

          x= 1/2 or 8

then y= 2(1/2)-4= -3  or y= 2(8)-4=12
by Diamond (38,769 points)

Related questions

0 like 0 dislike
1 answer

Welcome to MathsGee Q&A Bank, Africa’s largest personalized STEM and Financial Literacy education network that helps people find answers to problems, connect with others and take action to improve their outcomes.


MathsGee Q&A is the STEM and Financial Literacy knowledge-sharing community where students and experts put their heads together to crack their toughest questions.


MathsGee is free of annoying ads. We want to keep it like this. You can help with your DONATION

Enter your email address:

11,440 questions
9,430 answers
100 comments
10,398 users