First, expand both sides of the equation:
(2x−3b)2=4x2−12xb+9b2 (x+6b)(x−9b)(8x−12b)=(x2−9xb+6xb−54b2)(8x−12b)=(x2−3xb−54b2)(8x−12b)=8x3−12x2b−24x2b+36xb2−432xb2+648b3=8x3−36x2b−396xb2+648b3 (3b)3=27b3 Now we can substitute these expansions into the original equation:
4x2−12xb+9b2=8x3−36x2b−396xb2+648b3−27b3 4x2−12xb+9b2=8x3−36x2b−396xb2+621b3 Rearrange the equation to set it to zero:
0=8x3−36x2b−4x2−396xb2+12xb+621b3−9b2 0=8x3−(36b+4)x2+(12b−396b2)x+(621b3−9b2) This equation looks complicated. Let's reconsider our previous steps. The term (x+6b)(x−9b)(8x−12b)=(x+6b)(x−9b)4(2x−3b). Notice that (2x−3b) is present in the expansion of the left-hand side as well. Let's write (x+6b)(x−9b)(8x−12b)=(x+6b)(x−9b)4(2x−3b)=4(x2−3xb−54b2)(2x−3b)=4(2x3−3x2b−6x2b+9xb2−108xb2+162b3)=4(2x3−9x2b−99xb2+162b3)=8x3−36x2b−396xb2+648b3 So, we have 4x2−12xb+9b2=8x3−36x2b−396xb2+648b3−27b3 4x2−12xb+9b2=8x3−36x2b−396xb2+621b3 Rearranging:
8x3−36x2b−4x2−396xb2+12xb+621b3−9b2=0 8x3−(36b+4)x2+(12b−396b2)x+(621b3−9b2)=0 If the equation was (2x−3b)2=(x+6b)(x−9b)(8x−12b)−(3b)3, let us rewrite the right side: 4(x+6b)(x−9b)(2x−3b)−27b3. Let 2x−3b=y. Then x=(y+3b)/2. (x+6b)=(y+3b)/2+6b=(y+15b)/2 (x−9b)=(y+3b)/2−9b=(y−15b)/2 y2=4(2y+15b)(2y−15b)y−27b3 y2=(y2−225b2)y−27b3 y2=y3−225b2y−27b3 y3−y2−225b2y−27b3=0 We can express everything in terms of y now. Let us go back to the original equation. (2x−3b)2=(x+6b)(x−9b)(8x−12b)−(3b)3 (2x−3b)2=(x+6b)(x−9b)4(2x−3b)−27b3 Let y=2x−3b. Thus, x=(y+3b)/2 Then (x+6b)=(y+3b)/2+6b=(y+15b)/2 And (x−9b)=(y+3b)/2−9b=(y−15b)/2 y2=(2y+15b)(2y−15b)4y−27b3 y2=(y2−225b2)y−27b3 y2=y3−225b2y−27b3 y3−y2−225b2y−27b3=0. If we consider y=15b, 153b3−152b2−225b2(15b)−27b3=3375b3−225b2−3375b3−27b3=0 If we consider y=−3b, (−3b)3−(−3b)2−225b2(−3b)−27b3=−27b3−9b2+675b3−27b3=621b3−9b2=0 Let's try 2x−3b=0, x=3b/2. (0)=(23b+6b)(23b−9b)4(23b−23b)−27b3. 0=(215b)(2−15b)(0)−27b3 0=0−27b3 −27b3=0, so b=0. When b=0, (2x)2=x∗x∗8x−0 4x2=8x3, 4x2(2x−1)=0 x=0 or x=1/2. If b = 0, the equation reduces to 4x2=8x3, which simplifies to 2x3−x2=0, so x2(2x−1)=0. Thus x=0 or x=1/2.