Question

3. Expand the following cubes :
(1) (1 + x) ³
(ii) (1 - x)³
(it) (2x +3y)³
D) (x - 4y ) ³
(v) (3a + 4b) ³
(vi) (5p- 3q)³​

Answer 1

Answer:

3) (5p-3q)³

using identity 6th

(a-b)²=a³-b³-3ab(a-b)

(5p-3q)= (5p)³-(3q)³-3(5p)(3q)(5p-3q)

= 125p³-27q³-225p²q+135pq²

4) (x-4y)³

using identity 6th

(a-b)²=a³-b³-3ab(a-b)

(x-4y)³= (x)³-(4y)³-3(x)(4y)(x-4y)

= x³-64y³-12x²y+48xy²

5) (3a+4b)³

using identity 5th

(a+b)³=a³+b³+3ab(a+b)

(3a+4b)³= (3a)³+(4b)³+3(3a)(4b)(3a+4b)

= 27a³+64b³+108a²b+144ab²

6) (2x+3y)³

using identity 5th

(a+b)³=a³+b³+3ab(a+b)

(2x+3y)= (2x)³+(3y)³+3(2x)(3y)(2x+3y)

= 8x³+27y³+36x²y+54xy²