Question

If $(9/7{)}^3\times (49/81{)}^{2\times -6}=(7/9{)}^9$, then the value of x is?

• A. $12$
• B. $9$
• C. $8$
• D. $6$

Answer 1

Answer: (D)

$6$

${\left(\frac{9}{7}\right)}^3\times {\left(\frac{49}{81}\right)}^{2x-6}={\left(\frac{7}{9}\right)}^9$
${\left(\frac{7}{9}\right)}^{-3}\times {\left(\frac{7}{9}\right)}^{4x-12}={\left(\frac{7}{9}\right)}^9$
${\left(\frac{7}{9}\right)}^{4x-12-3}={\left(\frac{7}{9}\right)}^9$
$4x-15=9$
$4x=24$
$x=6$.