question_answer

Find the value of the following expressions, for a =3,b =2:

(a) a + b

(b) 7a-4b

(c) \[{{a}^{2}}+2ab+{{b}^{2}}\]

(d) \[{{a}^{3}}-{{b}^{3}}\]

Answer:

Substituting a = 3 and b = 2 in

(a) a + b, we get

a + b = 3 + 2 = 5 1

(b) 7a ? 4b, we get

7a ? 4b = 7 × 3 ? 4 × 2

= 21 ? 8 = 13

(c) \[{{a}^{2}}+2ab+{{b}^{2}}\], we get

\[{{a}^{2}}+2ab+{{b}^{2}}={{3}^{2}}+2\times 3\times 2+{{2}^{2}}\]

= 9 + 2 × 6 + 4

= 9 + 12 + 4 = 25. 1

(d)\[{{a}^{3}}{{b}^{3}}\], we get

\[{{a}^{3}}{{b}^{3}}={{3}^{3}}{{2}^{3}}=3\times 3\times 32\times 2\times 2\]

= 27 ? 8 = 19. 1