(1)24x^2+25x+6(2)-2m^2+7m-3(3)0.2x^2-3x+10(4)9x^4-82x^2+9(5)30x^3y+2x^2y^2-12xy^3我现在对第一项系数不为一的题目没辙.

Question

(1)24x^2+25x+6 (2)-2m^2+7m-3 (3)0.2x^2-3x+10 (4)9x^4-82x^2+9
(5)30x^3y+2x^2y^2-12xy^3
我现在对第一项系数不为一的题目没辙.

Answer 1

全部都用十字相乘法
8x + 3
3x + 2
16x + 9x = 25x
∴24x² + 25x + 6 = (8x + 3)(3x + 2)
- 2m + 1
m - 3
6m + m = 7m
∴- 2m² + 7m - 3 = (1 - 2m)(m - 3)
0.2x² - 3x + 10
= (1/5)(x² - 15x + 50)
x - 10
x - 5
- 5x - 10x = - 15x
∴0.2x² - 3x + 10 = 0.2(x - 10)(x - 5)
9x² - 1
x² - 9
- 81x² - x² = - 82x²
∴9x⁴ - 82x² + 9
= (x² - 9)(9x² - 1)
= (x + 3)(x - 3)(3x + 1)(3x - 1)
30x³y + 2x²y² - 12xy³
= 2xy(15x² + xy - 6y²)
5x - 3y
3x + 2y
10xy - 9xy = xy
∴30x³y + 2x²y - 12xy³ = 2xy(5x - 3y)(3x + 2y)