Câu hỏi của Sách Giáo Khoa

Question

Tính :

a) $\left(2+xy\right)^2$

b) $\left(5-3x\right)^2$

c) $\left(5-x^2\right)\left(5+x^2\right)$

d) $\left(5x-1\right)^3$

e) $\left(2x-y\right)\left(4x^2+2xy+y^2\right)$

f) \(\left(x...

Tuyết Nhi Melody · Accepted Answer

Bài giải:

a) (2 + xy)2 = 22 + 2 . 2 . xy + (xy)2 = 4 + 4xy + x2y2

b) (5 – 3x)2= 52 – 2 . 5 . 3x + (3x)2 = 25 – 30x + 9x2

c) (5 – x2)(5 + x2) = 52 – (x2)2 = 25 – x4

d) (5x – 1)3 = (5x)3 – 3 . (5x)2. 1 + 3 . 5x . 12 – 13 = 125x3 – 75x2 + 15x – 1

e) (2x – y)(4x2 + 2xy + y2) = (2x – y)[(2x)2 + 2x . y + y2] = (2x)3 – y3 = 8x3 – y3

f) (x + 3)(x2 – 3x + 9) = (x + 3)(x2 – 3x + 32) = x3 + 33 = x3 + 27.Câu trả lời: Bài giải:

a) (2 + xy)2 = 22 + 2 . 2 . xy + (xy)2 = 4 + 4xy + x2y2

b) (5 – 3x)2= 52 – 2 . 5 . 3x + (3x)2 = 25 – 30x + 9x2

c) (5 – x2)(5 + x2) = 52 – (x2)2 = 25 – x4

d) (5x – 1)3 = (5x)3 – 3 . (5x)2. 1 + 3 . 5x . 12 – 13 = 125x3 – 75x2 + 15x – 1

e) (2x – y)(4x2 + 2xy + y2) = (2x – y)[(2x)2 + 2x . y + y2] = (2x)3 – y3 = 8x3 – y3

f) (x + 3)(x2 – 3x + 9) = (x + 3)(x2 – 3x + 32) = x3 + 33 = x3 + 27.

Nào Ai Biết · Answer

a)

$\left(2+xy\right)^2=\left(4+x^2y^2+4xy\right)$

b)

$\left(5-3x\right)^2=25+9x^2-30x$

c)

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

d)

$\left(5x-1\right)^3=125x^3-1-75x^2+15x$

e)

$\left(2x-y\right)\left(4x^2+2xy+y^2\right)=8x^3-y^3$

f)

$\left(x+3\right)\left(x^2-3x+9\right)=x^3+27$Câu trả lời: a)

$\left(2+xy\right)^2=\left(4+x^2y^2+4xy\right)$

b)

$\left(5-3x\right)^2=25+9x^2-30x$

c)

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

d)

$\left(5x-1\right)^3=125x^3-1-75x^2+15x$

e)

$\left(2x-y\right)\left(4x^2+2xy+y^2\right)=8x^3-y^3$

f)

$\left(x+3\right)\left(x^2-3x+9\right)=x^3+27$

Bài 5: Những hằng đẳng thức đáng nhớ (Tiếp)