Question

Find the cube root of each of the following using (a+b)3=a3+3ab+3ab2+b3=12

Answer 1

Answer:

(i) 64

\sqrt[3]{64}=\sqrt[3]{2\times2\times2\times2\times2\times2}

3

64

=

3

2×2×2×2×2×2

\sqrt[3]{64}=\ 2\times2

3

64

= 2×2

= 415625

\sqrt[3]{15625}=\sqrt[3]{5\times5\times5\times5\times5\times5}

3

15625

=

3

5×5×5×5×5×5

= 5 x 5

= 25

(vi) 13824

\sqrt[3]{13824}=\sqrt[3]{2\times2\times2\times2\times2\times2\times2\times2\times2\times3\times3\times3}

3

13824

=

3

2×2×2×2×2×2×2×2×2×3×3×3

= 2 x 2 x 2 x 3

= 24Solve : x-21 = 0

Add 21 to both sides of the equation :

x = 21