Đáp án:
Giải thích các bước giải:
4.1
a, x² - 6x + 5 = x² - 5x - x + 5
= x(x - 5) - (x - 5)
= (x - 1)(x - 5)
b, x² + 6x + 8 = x² + 2x + 4x + 8
= x(x + 2) + 4(x + 2)
= (x + 4)(x + 2)
c, 2x² + 10x + 8 = 2x² + 2x + 8x + 8
= 2x(x + 1) + 8(x + 1)
= (2x + 8)(x+1)
= 2(x + 4)(x + 1)
d, 9x² + 6x - 8 = 9x² + 12x − 6x − 8
= 3x(3x + 4) − 2(3x + 4)
= (3x - 2)(3x + 4)
4.2
a, x² + 10x + 25 = x² + 5x + 5x + 25
= x(x + 5) + 5(x + 5)
= (x + 5)(x + 5) = (x + 5)²
b, 25x² - 20xy + 4y² = (5x)² - 2.5.2xy + (2y)²
= (5x - 2y)²
c, 9x^4 + 24x² + 1 = (3x²)² + 2.3x².1/2 + 1 + 21x²
= (3x² + 1/2)² + 21x²
