What is (x+9)(x^3+3x-8) 

3 Answers

justaguide's profile pic

justaguide | College Teacher | (Level 2) Distinguished Educator

Posted on

What has been given is not an equation but the product of two terms


=> x^4 + 9x^3 + 3x^2 + 27x - 8x - 72

If the equation to be solved is (x+9)(x^3+3x-8) = 0, equate each of the terms to 0.

x + 9 = 0

=> x = -9

x^3+3x-8 = 0 can be solved by factorization. The function provided in the link to find roots of a cubic equation has to be used. This gives the roots: `(sqrt(17)+4)^(1/3)*(-sqrt(3)*i/2-1/2)-(sqrt(3)*i/2-1/2)/(sqrt(17)+4)^(1/3)`, `(sqrt(17)+4)^(1/3)*(sqrt(3)*i/2-1/2)-(-sqrt(3)*i/2-1/2)/(sqrt(17)+4)^(1/3)` and `(sqrt(17)+4)^(1/3)-1/(sqrt(17)+4)^(1/3) `

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elekzy | Student, Grade 11 | (Level 1) Valedictorian

Posted on

multiply each term in the first bracket by each term in the second


collect like terms



You can use Pascal's Triangle to solve this.