a: =-29x(165-65)=-29x100=-2900

b: \(=\left[215-5\cdot30-60\right]:53=0\)

(14568+3579)-(14563+3564)

= 14568+3579-14563-3564

=(14568-14563)+(3579-3564)

=5+15=20

1) Ta có: \(x^2-4xy+4y^2\)

\(=x^2-2.x.2y+\left(2y\right)^2\)

\(=\left(x-2y\right)^2\)

Phép tính trở thành: \(\left(x-2y\right)^2:\left(x-2y\right)=x-2y\)

2) Ta có: \(25x^2+2xy+\dfrac{1}{25}y^2\)

\(=\left(5x\right)^2+2.5x.\dfrac{1}{5}y+\left(\dfrac{1}{5}y\right)^2\)

\(=\left(5x+\dfrac{1}{5}y\right)^2\)

Phép tính trở thành: \(\left(5x+\dfrac{1}{5}y\right)^2:\left(5x+\dfrac{1}{5}y\right)=5x+\dfrac{1}{5}y\)

1) (x² - 4xy + 4y²) : (x - 2y)

= (x - 2y)² : (x - 2y)

= x - 2y

2) (25x² + 2xy + 1/25 y²) : (5x + 1/5 y)

= 5x + 1/5 y)² : (5x + 1/5 y)

= 5x + 1/5 y

\(=20.\left(-9\right)+\left(-20\right).21\)

\(=-180+\left(-420\right)\)

\(=-600\)

a) =20.(-9)+(-20).21

=20.(-9)+20.(-21)

=20[(-9)+(-21)]

=20.(-30)

=-600

Cách 1: Theo kiểu dài                       |           Cách 2:Ngắn gọn
a) (29 – 9). (-9) + (-13 – 7). 21          |       a) (29-9) . (-9) + (-13-7) . 21
= 20. (-9) + [- (13 + 7). 21]                 |       =20.(-9)+(-20).21
= 20. (-9) + (-20). 21                          |       =180+(-420)
= (-20). 9 + (-20). 21                          |       =600
= (-20). (9 + 21)                                 |
= (-20). 30                                          |
= - (20. 30)                                         |
= - 600.                                              |

(Chúc bạn học tốt nha~!)

A=2,42x46+8x0,75+54x2,42+0,25x8

=(2,42x46+54x2,42)+(8x0,75+0,25x8)

=2,42(46+54)+8(0,75+0,25)

=2,42x100+8x1

=242+8

=250

(5x-1)²+(5x+1)²-2(1-25x²)=25x²-10x+1+25x²+10x+1-2-50x²

                                          = 0

Lời giải:

$(5x-1)^2+(5x+1)^2-2(1-25x^2)$

$=(5x-1)^2+(5x+1)^2-2(1-5x)(1+5x)$

$=(5x-1)^2+(5x+1)^2+2(5x-1)(5x+1)$

$=(5x-1+5x+1)^2$

$=(10x)^2=100x^2$

Ta có : \(\left(5x-1\right)^2-2\left(1-25x^2\right)+\left(5x+1\right)^2\)

\(=\left(5x-1\right)^2+2\left(25x^2-1\right)+\left(5x+1\right)^2\)

\(=\left(5x-1\right)^2+2\left(5x-1\right)\left(5x+1\right)+\left(5x+1\right)^2\)

\(=\left(5x-1+5x+1\right)^2=\left(10x\right)^2=100x^2\)