Question

Which of the following option is the simplest form of $3x^{4}y\times 7x^5{y}^{-3}?$

• A. $10x^9{y}^{-2}$
• B. $21x^9{y}^4$
• C. $21x^9{y}^{-2}$
• D. None of the above

Answer 1

The correct option is C $21x^9{y}^{-2}$

$3x^{4}y\times 7x^5{y}^{-3}$

$=(3\times 7)\times (x^4\times x^5)\times (y^1\times y^{-3})$

$=21\times x^{(4+5)}\times y^{1+(-3)}$
($\because a^m\times a^n=a^{(m+n)}$)

$=21\times x^9\times y^{-2}$

$=21x^9{y}^{-2}$

Therefore, option (c.) is the correct one.