你怎么找到4x ^ 3-4x ^ 2-9x + 9的所有零,1为零?

你怎么找到4x ^ 3-4x ^ 2-9x + 9的所有零,1为零?
Anonim

回答:

3根是 #x = -3 / 2,1,3 / 2#

注意我找不到长除法符号所以我将在它的位置使用平方根符号。

说明:

#F(X)= 4×^ 3-4倍^ 2-9x + 9#

#F(1)= 4 * 1 ^ 3-4 * 1 ^ 2-9 * 1 + 9 = 4-4-9 + 9 = 0#

这意味着x = 1是根和 #(X-1)# 是这个多项式的一个因素。

我们需要找到其他因素,我们通过将f(x)除以得到 #(X-1)# 找到其他因素。

#{4倍^ 3-4倍^ 2-9x + 9} / {X-1}#

#(X-1)的sqrt(4倍^ 3-4倍^ 2-9x + 9)#

以来 #(X * 4倍^ 2)= 4×^ 3# 我们得到 #4X ^ 2# 作为因素的一个术语

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #4X ^ 2#

#(X-1)的sqrt(4倍^ 3-4倍^ 2-9x + 9)#

我们需要找到其余部分以找到还需要找到的东西。

我们的确是 #4倍^ 2 *(X-1)= 4×^ 3-4倍^ 2#

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #4X ^ 2#

#(X-1)的sqrt(4倍^ 3-4倍^ 2-9x + 9)#

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #4倍^ 3-4倍^ 2#

我们减去这个得到0

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #4X ^ 2#

#(X-1)的sqrt(4倍^ 3-4倍^ 2-9x + 9)#

# # # # # # # # # # # # # # # # # # # # # # # # #ul { - (4x ^ 3-4x ^ 2)}#

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # ## # # # #0X ^ 3-0x ^ 2#

这个零意味着我们没有线性项,并且下一个条款。

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #4x ^ 2 + 0 x#

#(X-1)的sqrt(4倍^ 3-4倍^ 2-9x + 9)#

# # # # # # # # # # # # # # # # # # # # # # # # #ul { - (4x ^ 3-4x ^ 2)}#

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #0X ^ 3-0x ^ 2# #-9x + 9#

#X * -9 = -9x# 所以下一学期是 #-9#

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #4x ^ 2 + 0 x -9#

#(X-1)的sqrt(4倍^ 3-4倍^ 2-9x + 9)#

# # # # # # # # # # # # # # # # # # # # # # # # #ul { - (4x ^ 3-4x ^ 2)}#

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #0X ^ 3-0x ^ 2# #-9x + 9#

#-9 *(x-1)= - 9x + 9#

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #4x ^ 2 + 0 x -9#

#(X-1)的sqrt(4倍^ 3-4倍^ 2-9x + 9)#

# # # # # # # # # # # # # # # # # # # # # # # # #ul { - (4x ^ 3-4x ^ 2)}#

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #0X ^ 3-0x ^ 2# #-9x + 9#

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #ul { - ( - 9x + 9)}#

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #4x ^ 2 + 0 x -9#

#(X-1)的sqrt(4倍^ 3-4倍^ 2-9x + 9)#

# # # # # # # # # # # # # # # # # # # # # # # # #ul { - (4x ^ 3-4x ^ 2)}#

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #0X ^ 3-0x ^ 2# #-9x + 9#

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #ul { - ( - 9x + 9)}#

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #0#

所以 #(x-1)(4x ^ 2 -9)# 没有提醒(您可以通过扩展来检查)。我们需要完全考虑这一点。

#(4x ^ 2 -9)# 是因子与方格的差异 #(2X-3)*(2×+ 3)#

我们有 #(x-1)*(2x-3)*(2x + 3)= 0#

#2X-3 = 0# 给了我们一个根源 #X = 3/2##2X + 3 = 0# 给了我们一个根源 #X = -3 / 2#

根源是 #x = -3 / 2,1,3 / 2#