Question

x三次方加3x平方y- 4 x- 12y因式分解是多少？

Answer 1

f(x,y)= x^3+3x^2.y- 4x- 12y
f(-3y, y) = 27y^3+27y^3 +12y -12y =0
x^3+3x^2.y- 4x- 12y
=x^2. (x+3y) - 4x -12y
=x^2. (x+3y) - 4(x+3y)
=(x+3y)(x^2-4)
=(x+3y)(x-2)(x+2)