a) \(=y^4-81-y^4+4=-77\)

b) \(=a^2+b^2+c^2+2ab-2ac-2bc-a^2+2ac-b^2-2ab+2ac=c^2\)

c) Nhân 2 vào biểu thức

Bài 2: 

b: Ta có: \(x\left(x+4\right)\left(x-4\right)-\left(x^2+1\right)\left(x^2-1\right)\)

\(=x^3-4x-x^4+1\)

\(=-x^4+x^3-4x+1\)

c: Ta có: \(\left(a+b-c\right)^2-\left(a-c\right)^2-2ab+2ab\)

\(=\left(a+b-c-a+c\right)\left(a+b-c+a-c\right)\)

\(=b\left(2a+b-2c\right)\)

\(=2ab+b^2-2bc\)

\(a + b = -3\)   

\(ab = 2\)

Từ \(ab = 2\), ta có thể giải ra được \(a = \frac{2}{b}\) hoặc \(b = \frac{2}{a}\).

Đặt \(a = \frac{2}{b}\) vào \(a + b = -3\) ta được:   

\(\frac{2}{b} + b = -3\)  

\(2 + b^2 = -3b\)  

\(b^2 + 3b + 2 = 0\)  

\((b + 1)(b + 2) = 0\)  

\(b = -1\) hoặc \(b = -2\).

Khi \(b = -1\), ta có \(a = -2\). Khi \(b = -2\), ta có \(a = -1\).

Vậy giá trị của biểu thức \(A = a^3 + b^3\) khi \(a = -2, b = -1\) hoặc khi \(a = -1, b = -2\). 

\(1,\left(x+y\right)^2-\left(x-y\right)^2=\left[\left(x+y\right)-\left(x-y\right)\right]\left[\left(x+y\right)+\left(x-y\right)\right]=\left(x+y-x+y\right)\left(x+y+x-y\right)=2y.2x=4xy\)

\(2,\left(x+y\right)^3-\left(x-y\right)^3-2y^3\)

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

\(=6x^2y\)

\(3,\left(x+y\right)^2-2\left(x+y\right)\left(x-y\right)+\left(x-y\right)^2\\ =\left[\left(x+y\right)-\left(x-y\right)\right]^2\\ =\left(x+y-x+y\right)^2\\ =4y^2\)

\(4,\left(2x+3\right)^2-2\left(2x+3\right)\left(2x+5\right)+\left(2x+5\right)^2\\ =\left[\left(2x+3\right)-\left(2x+5\right)\right]^2\\ =\left(2x+3-2x-5\right)^2\\ =\left(-2\right)^2\\ =4\)

\(5,9^8.2^8-\left(18^4+1\right)\left(18^4-1\right)\\ =18^8-\left[\left(18^4\right)^2-1\right]\\ =18^8-18^8+1\\ =1\)

1: =x^2+2xy+y^2-x^2+2xy-y^2=4xy

2: =x^3+3x^2y+3xy^2+y^3-x^3+3x^2y-3xy^2+y^3-2y^3

=6x^2y

3: =(x+y-x+y)^2=(2y)^2=4y^2

4: =(2x+3-2x-5)^2=(-2)^2=4

5: =18^8-18^8+1=1

bạn viết có thánh đọc ra á :v

Bạn viết như vậy vẫn nhìn đc nhưng nhìn hơi khó

Thì các bạn vít ra giấy là hỉu nk mong giải giúp mk cái

16x^4_y2-25a²b²

1) \(x^6+1\)

\(=x^6+x^4-x^4+x^2-x^2+1\)

\(=\left(x^6-x^4+x^2\right)+\left(x^4-x^2+1\right)\)

\(=x^2\left(x^4-x^2+1\right)+\left(x^4-x^2+1\right)\)

\(=\left(x^2+1\right)\left(x^4-x^2+1\right)\)

2) \(x^6-y^6\)

\(=\left(x^3+y^3\right)\left(x^3-y^3\right)\)

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

3) \(5x^2y^4-10x^4y^2+5x^2y^2\)

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

4) \(25a^2-49b^2\)

\(=\left(5a+7b\right)\left(5a-7b\right)\)

5) \(36\left(x-y\right)^2-25\left(2x-1\right)^2\)

\(=\left[6\left(x-y\right)+5\left(2x-1\right)\right]\left[6\left(x-y\right)-5\left(2x-1\right)\right]\)

\(=\left[6x-6y+10x-5\right]\left[6x-6y-10x+5\right]\)

\(=\left(16x-6y-5\right)\left(-4x-6y+5\right)\)

b) \(3x\left(x-1\right)^2-2x\left(x+3\right)\left(x-3\right)+4x\left(x-4\right)\)

\(=3x\left(x^2-2x+1\right)-2x\left(x^2-9\right)+4x^2-16x=3x^3-6x^2+3x-2x^3+18x+4x^2-16x\)\(=x^3-2x^2+5x\)

c) \(2\left(2x+5\right)^2-3\left(4x+1\right)\left(1-4x\right)=2\left(4x^2+20x+25\right)+3\left(16x^2-1\right)\)

\(=8x^2+40x+50+48x^2-3=56x^2+40x+47\)

d) \(x\left(x+4\right)\left(x-4\right)-\left(x^2+1\right)\left(x^2-1\right)=x\left(x^2-16\right)-x^4+1=x^3-x^4-16x+1\)

e) \(\left(y-3\right)\left(y+3\right)\left(y^2+9\right)-\left(y^2+2\right)\left(y^2-2\right)=\left(y^2-9\right)\left(y^2+9\right)-y^4+4=y^4-81-y^2+4=-77\)

Khủng bố

a ) \(2\left(x-1\right)^2-4\left(3+x^2\right)+2x\left(x-5\right)\)

\(=2.\left(x^2-2.x.1+1^2\right)-12-4x^2+2x^2-10x\)

\(=2x^2-4x+2-12-4x^2+2x^2-10x\)

\(=-14x-10\)

Câu 5:B

Câu 4: C

Câu 3: D

Câu 2: A

Câu 1: A

a) Mình không hiểu đề cho lắm 

b) \(3x\left(x-1\right)^2-2x\left(x+3\right)\left(x-3\right)+4x\left(x-4\right)\)  

   \(=3x\left(x^2-2x+1\right)-2x\left(x^2-9\right)+4x\left(x-4\right)\) 

   \(=3x^3-6x^2+3x-2x^3+18x+4x^2-16x\)  

   \(=x^3-2x^2+5x\)  

c) \(2\left(2x+5\right)^2-3\left(4x+1\right)\left(1-4x\right)\)

   \(=2\left(2x+5\right)^2+3\left(4x+1\right)\left(4x-1\right)\)

    \(=2\left(4x^2+20x+25\right)+3\left(16x^2-1\right)\)

    \(=8x^2+40x+50+48x^2-3\)

    \(=56x^2+40x+47\)

d) \(x\left(x+4\right)\left(x-4\right)-\left(x^2+1\right)\left(x^2-1\right)\)

   \(=x\left(x^2-16\right)-\left(x^4-1\right)\)

   \(=x^3-16x-x^4+1\)

e) \(\left(y-3\right)\left(y+3\right)\left(y^2+9\right)-\left(y^2+2\right)\left(y^2-2\right)\)

    \(=\left(y^2-9\right)\left(y^2+9\right)-\left(y^4-4\right)\)

    \(=y^4-81-y^4+4\)

    \(=-77\)