Đáp án:
Giải thích các bước giải:
a) ( x + 5)²
= x² + 2.x.5 + 5² = x² + 10x + 25
b) ( y - 7)²
= y² - 2.y.7 + 7² = y² - 14y + 49
c) ( 2x + 3)²
= (2x)² + 2.2x.3 + 3² = 4x² +12x +9
d) ( 2y - 1)²
= ( 2y)² - 2.2y.1 + 1² = 4y² - 4y + 1
e) y² - 81 = y² - 9² = ( y - 9)( y + 9)
g) ( 3y + 2)³
= ( 3y)³ + 3.(3y)².2 + 3.3y.2² + 2³
= 27x³ + 54y² + 36y + 8
f) 16x² - 225 =( 4x)² - 15²
= ( 4x + 15)( 4x - 15)
h) ( 5x - 3)³
= ( 5x)³ - 3.(5x)².3 + 3.5x.3² - 3³
= 125x³ - 225x² + 135x - 27
l) ( 3x + 2y)³
=(3x)³ + 3.(3x)².2y + 3.3x.(2y)² + (2y)³
= 27x³ + 54x²y + 36xy² + 8y³
k) ( 2y - 1/2)³
= ( 2y)³ - 3.( 2y)².1/2 + 3.2y.(1/2)² - ( 1/2)³
= 8y³ - 6y² + 3/2y - 1/8
