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Algebra Level 1

81 1 / 2 × 81 3 / 2 = ? \LARGE {\color{#D61F06}{81}}^{-1/2} \large {\times \ } \LARGE{\color{#D61F06}{81}}^{3/2} = \ ?


The answer is 81.

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15 solutions

Elaine Zhang
Feb 11, 2015

We have the expression 8 1 1 / 2 × 8 1 3 / 2 81^{-1/2} \times 81^{3/2} . Using the rules of exponents , we have the above expression as \[\begin{array}{} & = 81^{-1/2 +3/2} \\ & = 81^1 \\ & = 81. \square \end{array}\]

Did it in the same way

Sonal Singh - 5 years, 9 months ago

Ahhhh, thank you

naveen naveen - 4 years, 4 months ago
Mohammad Saleem
Jul 9, 2015

When you multiply two numbers with powers, you add their exponents. So this comes out to be 2/2 which is 81^1

That's right!

Chung Kevin - 5 years, 10 months ago
Hyunmin Na
Jun 29, 2015

just -1 over 2 + 3 over 2 which is 1 so the answer is just 81^1 which is 81

Moderator note:

Good. It is easier to apply the rules of exponents to the powers first, rather than simplify each individual term.

Delano Might
Oct 9, 2015

8 1 1 2 × 8 1 3 2 = 8 1 1 2 + 3 2 = 8 1 2 2 = 8 1 1 = 81 81^{-\frac{1}{2}}\times81^{\frac{3}{2}} = 81^{-\frac{1}{2} + \frac{3}{2}}= 81^{\frac{2}{2}} = 81^1 = 81

محمد كذلك
Aug 26, 2015

just -1 over 2 + 3 over 2 which is 1 so the answer is just 81^1 which is 81

Mary Mitchell
Aug 7, 2015

3/2 - 1/2 = 2/2 = 1; 81^(1) = 81

Gustavo Milla
Jul 30, 2015

Leonardo Moncada
Jan 9, 2017

81^-1/2 x 81^3/2

1/81^1/2 x (81^1/2)^3

1/9 x 9^3

9^2

81

Huzaifa Abbas
Aug 6, 2015

81^-1/2 x 81^3/2

Take 81 common

81^3/2-1/2

81^2/2

81^1 = 81

Atika Kaleem
Jul 26, 2015

There is a rule of multiplication , that is if same bases are multiplying , then their powers will be added, so if we add -1/2+3/2 it will be equals to 1 and any no. Whose power is 1 will remain same .

Osama Fathy
Jul 26, 2015

8 1 1 / 2 × 8 1 3 / 2 = 8 1 3 / 2 1 / 2 = 81 81^{-1/2}\times81^{3/2} = 81^{3/2 - 1/2} = 81

Prashant Deokar
Jul 26, 2015

=(81^-1/2)*(81^3/2) =81^((-1/2)+(3/2)) =81

Ranti Rahmawati
Jul 26, 2015

1/2 + 3/2 = 2/2 = 1 so 81^1 = 81

Kyle Pilar
Mar 8, 2015

First(81^-1/2 )(81^3/2)=81^(-1/2+3/2)=81^2/2= 81^1=81

Aljun Bulado
Feb 18, 2015

81^(3/2-1/2) = 81

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