The zeros of the polynomial

Question:

The zeros of the polynomial $7 x^{2}-\frac{11}{3} x-\frac{2}{3}$ are

(a) $\frac{2}{3}, \frac{-1}{7}$

(b) $\frac{2}{7}, \frac{-1}{3}$

(c) $\frac{-2}{3}, \frac{1}{7}$

(d) none of these

 

Solution:

(a) $\frac{2}{3}, \frac{-1}{7}$

Let $f(x)=7 x^{2}-\frac{11}{3} x-\frac{2}{3}=0$

$\Rightarrow 21 x^{2}-11 x-2=0$

$\Rightarrow 21 x^{2}-14 x+3 x-2=0$

$\Rightarrow 7 x(3 x-2)+1(3 x-2)=0$

$\Rightarrow(3 x-2)(7 x+1)=0$

$\Rightarrow x=\frac{2}{3}$ or $x=\frac{-1}{7}$

 

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