Law 3: Power on a power Suppose we had a4 That is (a4
)3 . This means a4
and we want to raise it all to the power 3. × a4
× a4
Our fi rst rule tells us that we should add the indices together, which is 12 . But note also that 12 is 4 × 3. This suggests that if we have ap
powers to get ap × q , or simply a pq
all raised to the power q the result is obtained by multiplying the two .
Law 3: The third law tells us that when we have a number in index form and we want to raise it to a power, we multiply the two powers together to get the fi nal answer in index form. (ap) q
= ap × q The formula appears in the formulae and tables booklet.
Worked example Simplify the following leaving your answer in index form. (i)
(43 )2 Solution (ii) (iii) (ii) (x5 )4
(iii) ( y9
)2
Practice questions 19.4
1. Simplify the following, leaving your answers in index form. (i)
( 2 3 (y2 )2 )8 (ii) ( 5 4 )3 (ii) (a)5 (u7 )3 (ii) (p6 (iii) ( 6 3 )4 (iii) (b2 (iii) (n7 )2
2. Simplify the following, leaving your answers in index form. (i)
3. Simplify the following, leaving your answers in index form. (i)
)2
_____ x2
× x4 (ii) x6
_____ x5
× x9 (iii) m3 )3
______ m2
× m × m
4. Simplify the following, leaving your answers in index form. (i) x3