a) 79 + 1 011 = 79 + ( 1 010 + 1) = (79 + 1) + 1 010 = 80 + 1 010 = 1 090.

b) 292 + 20 008 + 250

= 292 + (20 000 + 8) + 250

= (292 + 8) + 20 000 + 250

= 300 + 20 000 + 250

= 20 550.

c) 1 811 + 15 + 189 + 185

= (1 800 + 11) + (15 + 185) + 189

= 1 800 + (11 + 189) + (15 + 185)

= 1 800 + 200 + 200

= 2 200.

A 17+188+183

=17+183+188

=   200   +188

=         388

B 122+2116+278+84

=122+278+2116+84

=    400    +    2200

=         2600

a)(17+183)+188=200+188=388

a) 9x²y² - 6xy² + y² 

= y²(9x² - 6x + 1) 

= y²(3x - 1)²

b) x³ + 27 - 3x(x + 3) 

 = (x + 3)(x² - 3x + 9) - 3x(x + 3)

= (x + 3)(x² - 6x + 9) 

= (x + 3)(x - 3)²

c) x² - 2x - 4y² - 4y

= x² - 2x + 1 - 4y² - 4y - 1 

= (x - 1)² - (2y + 1)²

= (x + 2y)(x - 2y - 2)

d) a⁴ - 2a²b² + b⁴ 

= (a² - b²)² 

 = [(a - b)(a + b)]² 

9x²y² - 6xy² + y² = ( 3xy - y )² = y² ( 3x - 1 )²

x³ + 27 - 3x(x + 3 ) = ( x + 3 ) ( x² - 3x + 9) - 3x ( x + 3 )

= ( x + 3 ) ( x² - 6x + 9 )

= ( x + 3 ) ( x - 3 ) ²

x² - 2x - 4y² - 4y = ( x - 2y ) ( x + 2y ) - 2 ( x + 2y ) = ( x + 2y ) ( x - 2y - 2 )

a⁴ - 2a²b² + b⁴ = ( a² - b² )² = ( a - b )² ( a + b )²

\(2a:2=4\)

\(2a=4.2\)

\(2a=8\)

\(a=8:2\)

\(=>a=4\)

\(2:2=1\)

1000x2x5x100=1000000

1000.2.5.100=1000.10.100=10³.10.10²=10³⁺¹⁺²= 10⁶

\(\sqrt{2x+1}=3\)ĐK : x > = -1/2 

\(\Leftrightarrow2x+1=9\Leftrightarrow2x=8\Leftrightarrow x=4\)( tm ) 

x=4 nha 

99- 97 + 95 – 93 + 91 – 89 + ... + 7 - 5 + 3 -1

= ( 99 - 97 ) + ( 95 – 93) + (91 – 89) + ... + (7 - 5 ) + (3 - 1)

= 2 + 2+ 2 + ...+ 2 + 2 (có 25 số 2)

= 2.25

= 50

giải

=99-97+95-93+91-89+...+7-5+3-1

có 25 số 2

=2.25

=50