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One factor of x^3 + 1331 is x + 11.
What is the value of the other factor when x = 3?

1 Answer

5 votes

Answer: 97

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Step-by-step explanation

Let,

  • f(x) = x^3 + 1331
  • g(x) = x+11 = one factor
  • h(x) = the other factor

The three items form this equation.

f(x) = g(x)*h(x)

Factors g(x) and h(x) multiply to get f(x).

You can use polynomial long division, or synthetic division, to determine h(x) and then plug in x = 3.

However, I'll use another approach.

Since all we care about is h(x) when x = 3, we can plug this value into x of the other functions.

f(x) = x^3 + 1331

f(3) = 3^3 + 1331

f(3) = 1358

g(x) = x+11

g(3) = 3+11

g(3) = 14

Then,

f(x) = g(x)*h(x)

f(3) = g(3)*h(3)

1358 = 14*h(3)

h(3) = 1358/14

h(3) = 97 is the value of the other factor when x = 3.

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Another approach:

1331 = 11^3

x^3+1331 = x^3+11^3 = sum of cubes

Use the sum of cubes factoring formula

x^3+11^3 = (x+11)(x^2-11x+11^2)

x^3+1331 = (x+11)(x^2-11x+121)

We see that x+11 is one factor, which matches the instructions.

The other factor is x^2-11x+121

h(x) = x^2-11x+121

h(3) = 3^2-11(3)+121

h(3) = 97 is the value of the other factor when x = 3.

User Howard Hodson
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