a: A=3(x^2-y^2)-2(x-y)^2

=3(x+y)(x-y)-2(x-y)^2

=(x-y)(3x+3y-2x+2y)

=(x-y)(x+5y)

=(4+4)(4-5*4)

=8*(-16)=-128

b: \(B=\left(2x-4\right)^2+2\cdot\left(2x-4\right)\left(x+1\right)+\left(x+1\right)^2\)

=(2x-4+x+1)^2

=(3x-3)^2

Khi x=-1/2 thì B=(-3/2-3)^2=(-9/2)^2=81/4

c: \(C=x^2\left(5-4\right)+y^2\left(4-6\right)+z^2\left(6+4\right)\)

=x^2-2y^2+10z^2

=6^2-2*5^2+10*4^2

=146

d: x=9 thì x+1=10

\(D=x^{2017}-x^{2016}\left(x+1\right)+x^{2015}\left(x+1\right)-...-x^2\left(x+1\right)+x\left(x+1\right)-\left(x+1\right)\)

=x^2017-x^2017+x^2016+...-x^3-x^2+x^2+x-x-1

=-1

a: A=3(x^2-y^2)-2(x-y)^2

=3(x+y)(x-y)-2(x-y)^2

=(x-y)(3x+3y-2x+2y)

=(x-y)(x+5y)

=(4+4)(4-5*4)

=8*(-16)=-128

\(A=x^3-xy-x^3-x^2y+x^2y-xy=-2xy\\ A=-2\cdot\dfrac{1}{2}\left(-100\right)=100\)

a.

\(M=x^2+4y^2-4xy=\left(x-2y\right)^2=\left(18-4.2\right)^2=10^2=100\)

b.

\(N=\left(2x\right)^3-3.\left(2x\right)^2.y-3.2x.y^2-y^3=\left(2x-y\right)^3=\left(2.6-\left(-8\right)\right)^3\)

\(=20^3=8000\)

A=x^2+6x+9+1

=(x+3)^2+1

Thay x=-103 vào A, ta được:

A=(-103+3)^2+1=10000+1=10001

\(a,A=x^2+6x+10\)

\(=\left(x^2+2\cdot x\cdot3+3^2\right)+1\)

\(=\left(x+3\right)^2+1\)

Thay \(x=-103\) vào \(A\), ta được:

\(A=\left(-103+3\right)^2+1\)

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

\(=10000+1\)

\(=10001\)

#Urushi

gúp mình với

A = x ( x + y ) - y ( x + y )

A = ( x + y ) ( x - y )

A = x\(^2\) - y\(^2\)

Tại x = \(\dfrac{-1}{2}\) và y = -2 ta có 

\(\left(\dfrac{-1}{2}\right)^2-\left(-2\right)^2\) \(=\) \(\dfrac{-15}{4}\)

\(A=x\left(x+y\right)-y\left(x+y\right)\)

\(=\left(x+y\right)\left(x-y\right)\)

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

Thay \(x=-\dfrac{1}{2}\) và \(y=-2\) vào biểu thức \(A\), ta có:

\(A=\left(-\dfrac{1}{2}\right)^2-\left(-2\right)^2\)

\(=\dfrac{1}{4}-4\)

\(=-\dfrac{15}{4}\)

Ta có:

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

Thay \(x=-3\) vào A, ta có:

\(A=2.\left(-3\right)^2=18\)

Vậy A=18

\(A=x\left(x+y\right)-x\left(y-x\right)=x\left(x+y\right)+x\left(x+y\right)=\left(x+y\right).2x=\left(-3+2\right).2.\left(-3\right)=6\)

Giúp vs ạ

`a)100x^2-20x+1`

`=(10x-1)^2`

Thay `x=1/10`

`=>100x^2-20x+1=(1-1)^2=0`

`b)49x^2-42x+10`

`=49*4/49-42*2/7+10`

`=4-12+10=2`

`c)25x^2+40x+16y^2`

`=(5x+4y)^2=(2+3)^2=25`

1)-14

2)110

3)123

1/ -14

2/ 110

3/ 0

4/ -66

1)     Với x = 2010, ta được:

2018 + 8 – 2018 – 22

= 2026 – 2018 – 22

= 8 – 22

= - 14

2)     Với x = - 98; a = 99, ta được:

= - 98 – 99 + 12 + 99

= [(-99) + 99] – 98 + 12

= 0 – 98 + 12

= (-98) + 12

= - 86

3)     Với a = 1; m = -123

= 1 – (- 123) + 7 – 8 + (-123)

= 124 + 7 – 8 + (- 123)

=  131 – 8 + (-123)

= 123 + (-123)

= 0

4)     Với y = -24, ta được:

= (-90) – ( -24 +10 ) + 100

= (-90) + 24 – 10 + 100

= [(-90) – 10] + 100 + 24

= (-100) + 100 + 24

= 0 + 24

= 24

 Đúng thì nhớ k cho mik nha, mik chỉ mới làm.