Toán Lớp 8: Phân tích đa thức thành nhân tử : a, 2x^3y-4xy b, (x+1)(x+2)(x+3)(x+4)-24

Question

Toán Lớp 8:  Phân tích đa thức thành nhân tử : a, 2x^3y-4xy b, (x+1)(x+2)(x+3)(x+4)-24

dongoclandiem · Answer

y10000   a )   2x&sup3;y - 4xy   = 2xy . ( x&sup2; - 2 )   b )   ( x + 1 ) . ( x + 2 ) . ( x + 3 ) . ( x + 4 ) - 24   = ( x&sup2; + 2x +x + 2 ) . ( x&sup2; + 4x + 3x + 12 ) - 24   = ( x&sup2; + 3x + 2 ) . ( x&sup2; + 7x + 12 ) - 24   = x⁴ + 7x&sup3; + 12x&sup2; + 3x&sup3; + 21x&sup2; + 36x + 2x&sup2; + 14x + 24 - 24   = x⁴ + 10x&sup3; + 35x&sup2; + 50x   = x . ( x&sup3; + 10x&sup2; + 35x + 50 )

dananhnhu2k4 · Answer

a)2x^3y-4xy   =2xy.(x^2-2)   b)(x+1).(x+2).(x+3).(x+4)-24   =[(x+1).(x+4)].[(x+2).(x+3)]-24   =(x^2+4x+x+4).(x^2+3x+2x+6)-24   =(x^2+5x+4).(x^2+5x+6)-24   =[(x^2+5x+5-1).(x^2+5x+5+1)]-24   =[(x^2+5x+5)^2-1^2]-24   =(x^2+5x+5)^2-1-24   =(x^2+5x+5)^2-25   =(x^2+5x+5-5).(x^2+5x+5+5)   =(x^2+5x).(x^2+5x+10)   =x.(x+5).(x^2+5x+10)   &aacute;p dụng hđt:   (A+B).(A-B)^2=A^2-B^2   $#ch&uacute;c tus học tốt!!$   #La