College Algebra 7th Edition

Published by Brooks Cole
ISBN 10: 1305115546
ISBN 13: 978-1-30511-554-5

Chapter 3, Polynomial and Rational Functions - Section 3.4 - Real Zeros of Polynomials - 3.4 Exercises - Page 320: 39

Answer

The rational zeros are $x=2$ or $x=-1$ or $x=\frac{1}{2}$. The polynomial in factored form is $(x-2)^2(x+1)(2x-1)$.

Work Step by Step

Alternate form: $2x^4-7x^3+3x^2+8x-4 = (x-2)^2(2x^2+x-1)$ Solve for $x$ over the real numbers: $(x-2)^2(2x^2+x-1) = 0$ Split into two equations: $(x-2)^2=0$ or $2x^2+x-1=0$ Take the square root of both sides: $x-2=0$ or $2x^2+x-1=0$ Add $2$ to both sides: $x=2$ or $2x^2+x-1=0$ The left hand side factors into a product with two terms: $x=2$ or $(2x-1)(x+1)=0$ Split into two equations: $x=2$ or $x+1=0$ or $2x-1=0$ Subtract $1$ from both sides: $x=2$ or $x=-1$ or $2x-1=0$ Add $1$ to both sides: $x=2$ or $x=-1$ or $2x=1$ Answer: The rational zeros are $x=2$ or $x=-1$ or $x=\frac{1}{2}$. The polynomial in factored form is $(x-2)^2(x+1)(2x-1)$.
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