1, (a - b)^2 (2a - 3b) - (b - a)^2 (3a - 5b) + (a + b)^2 (a - 2b)
2, x^4 - 4(x^2 + 5) - 25
3, (2 - x)^2 + (x - 2)(x + 3) - (4x^2 - 1)
4, (4x^2 - y^2) - 8(x - ay) - 4(4a^ - 1)
5, 16(xy + 6)^2 - (4x^2 + y^2 - 25)^2
6, (x + y - 2z)^2 + (x + y + 2z)^2 - 16z^2
7,(ax + 3y)^2 - (1 - 6a)(x^2 + y^2) + (3x - ay)^2
dài quá, làm từ từ nhé
1, \(\left(a-b\right)^2\left(2a-3b\right)-\left(b-a\right)^2\left(3a-5b\right)+\left(a+b\right)^2\left(a-2b\right)\)
\(=\left(a-b\right)^2\left(2a-3b-3a+5b\right)+\left(a+b\right)^2\left(a-2b\right)\)
\(=\left(a-b\right)^2\left(-a+2b\right)+\left(a+b\right)^2\left(a-2b\right)\)
\(=-\left(a-b\right)^2\left(a-2b\right)+\left(a+b\right)^2\left(a-2b\right)\)
\(=\left(a-2b\right)\left[\left(a+b\right)^2-\left(a-b\right)^2\right]\)
\(=\left(a-2b\right)\left(a+b-a+b\right)\left(a+b+a-b\right)\)
\(=4ab\left(a-2b\right)\)
2, \(x^4-4\left(x^2+5\right)-25=\left(x^2-25\right)-4\left(x^2+5\right)=\left(x^2-5\right)\left(x^2+5\right)-4\left(x^2+5\right)\)
\(=\left(x^2-9\right)\left(x^2+5\right)=\left(x-3\right)\left(x+3\right)\left(x^2+5\right)\)
3,\(\left(2-x\right)^2+\left(x-2\right)\left(x+3\right)-\left(4x^2-1\right)=\left(x-2\right)^2+\left(x-2\right)\left(x+3\right)-\left(4x^2-1\right)\)
\(=\left(x-2\right)\left(x-2+x+3\right)-\left(2x-1\right)\left(2x+1\right)\)
\(=\left(x-2\right)\left(2x+1\right)-\left(2x-1\right)\left(2x+1\right)\)
\(=\left(x-2-2x+1\right)\left(2x+1\right)\)
\(=\left(-x-1\right)\left(2x+1\right)\)
4, câu này đề thiếu
5,\(16\left(xy+6\right)^2-\left(4x^2+y^2-25\right)^2=\left(4xy+24\right)^2-\left(4x^2+y^2-25\right)^2\)
\(=\left(4xy+24-4x^2-y^2+25\right)\left(4xy+24+4x^2+y^2-25\right)\)
\(=\left[49-\left(4x^2-4xy+y^2\right)\right]\left[\left(4x^2+4xy+y^2\right)-1\right]\)
\(=\left[49-\left(2x-y\right)^2\right]\left[\left(2x+y\right)^2-1\right]\)
\(=\left(7-2x+y\right)\left(7+2x-y\right)\left(2x+y-1\right)\left(2x+y+1\right)\)