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How to find the a in the equation y=ax^3 + d given the two points (0,10), (2,20)

User Stray
by
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2 Answers

5 votes
  • y=ax³+d

Put(0,10)

  • 10=a(0)³+d
  • d=10

Now

Put again (2,20) this time

  • 20=2³a+10
  • 10=8a
  • a=10/8
  • a=5/4
User Encee
by
3.5k points
6 votes

Answer:


y=(5)/(4)x^3+10

Explanation:

Given information:


  • y=ax^3+d
  • (0, 10)
  • (2, 20)

Create two equations by substituting the given points into the given equation:

Equation 1: point (0, 10)


\implies a(0)^3+d=10


\implies 0+d=10


\implies d=10

Equation 2: point (2, 20)


\implies a(2)^3+d=20


\implies 8a+d=20

Substitute Equation 1 into Equation 2 and solve for a:


\implies 8a+d=20


\implies 8a+10=20


\implies 8a+10-10=20-10


\implies 8a=10


\implies (8a)/(8)=(10)/(8)


\implies a=(10)/(8)


\implies a=(5)/(4)

Finally, substitute the found values of a and d into the original formula:


\implies y=(5)/(4)x^3+10

Check by substituting the x-values of the two given points into the found equation:


x=0 \implies y=(5)/(4)(0)^3+10=10 \leftarrow \textsf{correct}


x=2 \implies y=(5)/(4)(2)^3+10=20 \leftarrow \textsf{correct}

User Jianpx
by
3.7k points