hằng đẳng thức đáng nhớ

Bài 1. Triển khai các biểu thức sau theo hằng đẳng thức: 1) \(x^2-4 = (x+2)(x-2)\) 2) \(1-4x^2 = -(2x+1)(2x-1)\) 3) \(4x^2-9 = (2x+3)(2x-3)\) 4) \(9-25x^2 = (5x+3)(5x-3)\) 5) \(4x^2-25 = (2x+5)(2x-5)\) 6) \(9x^2-36 = 9(x+2)(x-2)\) 7) \(3x^2-y^2 = (x+y)(x-y)\) 8) \(x^2-2y^2 = (x+\sqrt{2}y)(x-\sqrt{2}y)\) 9) \(2x^2-y^2 = (x+\sqrt{2}y)(x-\sqrt{2}y)\) 10) \(3x^2-9y^4 = 3(x+3y^2)(x-3y^2)\) 11) \(16x^2-y^2 = (4x+y)(4x-y)\) 12) \(x^4-3y^2 = (x^2+\sqrt{3}y)(x^2-\sqrt{3}y)\) 13) \(2x+12x-1 = 14x-1\) 14) \(x-2y^2+x = 2x-2y^2\) 15) \(5x-3y^3+5x = 10x-3y^3\) 16) \((2x+\frac35)(\frac35-2x) = -\frac{4}{25}\) 17) \((\frac12x-\frac43)(\frac43+\frac12x) = -\frac{16}{9}\) 18) \((\frac23x^2-\frac y2)(\frac23x^2+\frac y2) = \frac49x^4-\frac14y^2\) Đáp án: 1) \(x^2-4 = (x+2)(x-2)\) 2) \(1-4x^2 = -(2x+1)(2x-1)\) 3) \(4x^2-9 = (2x+3)(2x-3)\) 4) \(9-25x^2 = (5x+3)(5x-3)\) 5) \(4x^2-25 = (2x+5)(2x-5)\) 6) \(9x^2-36 = 9(x+2)(x-2)\) 7) \(3x^2-y^2 = (x+y)(x-y)\) 8) \(x^2-2y^2 = (x+\sqrt{2}y)(x-\sqrt{2}y)\) 9) \(2x^2-y^2 = (x+\sqrt{2}y)(x-\sqrt{2}y)\) 10) \(3x^2-9y^4 = 3(x+3y^2)(x-3y^2)\) 11) \(16x^2-y^2 = (4x+y)(4x-y)\) 12) \(x^4-3y^2 = (x^2+\sqrt{3}y)(x^2-\sqrt{3}y)\) 13) \(2x+12x-1 = 14x-1\) 14) \(x-2y^2+x = 2x-2y^2\) 15) \(5x-3y^3+5x = 10x-3y^3\) 16) \((2x+\frac35)(\frac35-2x) = -\frac{4}{25}\) 17) \((\frac12x-\frac43)(\frac43+\frac12x) = -\frac{16}{9}\) 18) \((\frac23x^2-\frac y2)(\frac23x^2+\frac y2) = \frac49x^4-\frac14y^2\)