College Algebra (11th Edition)

Published by Pearson
ISBN 10: 0321671791
ISBN 13: 978-0-32167-179-0

Chapter 5 - Section 5.2 - Matrix Solution of Linear Systems - 5.2 Exercises - Page 500: 50

Answer

$A = \frac{4}{3}; B = \frac{2}{3}$

Work Step by Step

The given equation is: $$\dfrac{2x}{(x+2)(x-1)} =\dfrac{A}{(x+2)}+\dfrac{B}{(x-1)} ~~~(1)$$ On multiplying equation (1) with $(x+2) (x-1)$, we obtain: $$2x =A(x-1)+B(x+2)~~~(2)$$ Now, we will put $x=1$ in equation (2) to eliminate $A$ as follows: $$2(1) =A(1-1)+B(1+2)\\ B=\dfrac{2}{3}$$ Next, we will put $x=-2;$ in equation (2) to eliminate $B$ as follows: $$2(-2) =A(-2-1)+B(-2+2)\\ A=\dfrac{4}{3}$$ Solve equations (3) and (4) to obtain: $$A = \dfrac{4}{3}; B = \dfrac{2}{3}$$
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