8x3+y3+64-24xy factorize..?

2 Answers
Jun 12, 2018

Below

Explanation:

8x^3+y^3+64-24xy8x3+y3+6424xy

There are quite a number of solutions to this. If this is part of a question, you need to see which factorisation suits the question the best

You can have

(8x^3+64)+(y^3-24xy)(8x3+64)+(y324xy)
=8(x^3+8)+y(y^2-24x)8(x3+8)+y(y224x)
=8(x+2)(x^2-2x+4)+y(y^2-24x)8(x+2)(x22x+4)+y(y224x)

OR

(8x^3-24xy)+(y^3+64)(8x324xy)+(y3+64)
=8x(x^2-3y)+(y+4)(y^2-4y+16)8x(x23y)+(y+4)(y24y+16)

OR

(8x^3+y^3)+(64-24xy)(8x3+y3)+(6424xy)
=(2x+y)(4x^2-2xy+y^2)+8(8-3xy)(2x+y)(4x22xy+y2)+8(83xy)

Jun 13, 2018

Please refer to the Explanation.

Explanation:

If one is familiar with the following factorisation, then the

solution can easily be obtained :

a^3+b^3+c^3-3abc=(a+b+c)(a^2+b^2+c^2-ab-bc-ca).a3+b3+c33abc=(a+b+c)(a2+b2+c2abbcca).

:. "The Expression (exp.)="8x^3+y^3+64-24xy,

=(2x)^3+(y)^3+(4)^3-3(2x)(y)(4),

=(2x+y+4){(2x)^2+(y)^2+(4)^2-(2x)(y)-(y)(4)-(4)(2x)},

=(2x+y+4)(4x^2+y^2+16-2xy-4y-8x), is the

desired factorisation!

Otherwise :

Suppose that, 2x+y=u.

:. (2x+y)^3=u^3.

:. (2x)^3+y^3+3(2x)(y)(2x+y)=u^3," &, as, "2x+y=u,

8x^3+y^3+6uxy=u^3,

or, 8x^3+y^3=u^3-6uxy.

Adding (64-24xy) on both sides, we get,

8x^3+y^3+64-24xy=u^3-6uxy+64-24xy,

={(4)^3+(u)^3}-6uxy-24xy,

={color(red)((4+u))(4^2-4u+u^2)}-6xycolor(red)((u+4)),......[because, m^3+n^3=(m+n)^3-3mn(m+n)],

=(u+4){(16-4u+u^2)-6xy},

={(2x+y)+4}{16-4(2x+y)+(2x+y)^2-6xy}......[because, u=(2x+y)],

=(2x+y+4){16-8x-4y+4x^2+4xy+y^2-6xy},

=(2x+y+4)(4x^2+y^2+16-8x-4y-2xy), as before!

Enjoy Maths.!