Toán Lớp 8: giúp mik với a.8x^3-64 b.1+8x^6y^3 c.125x^3+1 d.8x^3-27 f.125x^3+27y^3 e.27x^3+y^3/8

Question

Toán Lớp 8:  giúp mik với a.8x^3-64 b.1+8x^6y^3 c.125x^3+1 d.8x^3-27 f.125x^3+27y^3 e.27x^3+y^3/8

thanhmaianh · Answer

a) 8x^3-64 = (2x)^3 - 4^3 = (2x-4)(x^2 +8x + 16)=2(x-2)(x^2+8x+16)     b) 1+8x^6y^3 = 1^3 + (2x^2y)^3= (1+2x^2y)(1 - 2x^2y + 4x^4y^2)     c) 125x^3+1 = (5x)^3 + 1^3 = (5x+1)(25x^2 - 5x + 1)     d) 8x^3-27 = (2x)^3 - 3^3 = (2x-3)(4x^2 + 6x + 9)     f) 125x^3 + 27y^3 = (5x)^3 + (3y)^3 = (5x+3y)(25x^2 - 15xy + 9y^2)     e)   27x^3+y^3/8 = (3x)^3 + (y/2)^3 = (3x+y/2)(9x^2 - (3xy)/2 + y^2/4)

tuyen98 · Answer

a) 8x&sup3; - 64   = 8(x&sup3; - 64)   = 8[(x)&sup3; - (2)&sup3;]   = 8(x - 2)(x&sup2; + 2x + 4)   b) 1 + 8$x^{6}$y&sup3;   = (1)&sup3; + (2x&sup2;y)&sup3;   = (1 + 2x&sup2;y)(1 - 2x&sup2;y + 4$x^{4}$y&sup2;)   c) 125x&sup3; + 1   = (5x)&sup3; + (1)&sup3;   = (5x + 1)(25x&sup2; - 5x + 1)   d) 8x&sup3; - 27   = (2x)&sup3; - (3)&sup3;   = (2x - 3)(4x&sup2; + 6x + 9)   f) 125x&sup3; + 27y&sup3;   = (5x)&sup3; + (3y)&sup3;   = (5x + 3y)(25x&sup2; - 15xy + 9y&sup2;)   e) 27x&sup3; + $ frac{y&sup3;}{8}$   = (3x)&sup3; + ($ frac{y}{2}$)&sup3;   = (3x + $ frac{y}{2}$)(9x&sup2; - $ frac{3xy}{2}$ + $ frac{y&sup2;}{4}$)      Ch&uacute;c bạn học tốt