\(a,4x^2+28x+49=\left(2x\right)^2+2.2x.7+7^2=\left(2x+7\right)^2\\ b,16y^2-8y+1=\left(4y\right)^2-2.4y.1+1^2=\left(4y-1\right)^2=\left(1-4y\right)^2\\ 4a^2+20ab+25b^2=\left(2a\right)^2+2.2a.5b+\left(5b\right)^2=\left(2a+5b\right)^2\\ d,9x^2-6xy+y^2=\left(3x\right)^2-2.3x.y+y^2=\left(3x-y\right)^2=\left(y-3x\right)^2\)

a) \(7x^2-63y^2\)

\(=7\cdot\left(x^2-9y^2\right)\)

\(=7\left[x^2-\left(3y\right)^2\right]\)

\(=7\left(x-3y\right)\left(x+3y\right)\)

b) \(36-4a^2+20ab-25b^2\)

\(=36-\left(4a^2-200ab+25b^2\right)\)

\(=6^2-\left(2a-5b\right)^2\)

\(=\left(6-2a+5b\right)\left(6+2a-5b\right)\)

c) \(2x-2y-x^2+2xy-y^2\)

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

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

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

a: =7(x^2-9y^2)

=7(x-3y)(x+3y)

b: =36-(4a^2-20ab+25b^2)

=36-(2a-5b)^2

=(6-2a+5b)(6+2a-5b)

c: =2(x-y)-(x-y)^2

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

a)7x² + 6x - 13

= 7x² - 7x + 13x - 13

= (7x² - 7x) + (13x - 13)

= 7x(x - 1) + 13(x - 1)

= (7x + 13)(x - 1)

b) 15(x - y) - 25x + 25y

= 15(x - y) - (25x - 25y)

= 15(x - y) - 25(x - y)

= (15 - 25)(x - y)

= -10(x - y)

c) 36 - 4a² + 20ab - 25b²

= 36 - (4a² - 20ab + 25b²)

= 6² - (2a - 5b)²

= (6 - 2a + 5b)(6 + 2a - 5b)

= (5b - 2a + 6)(2a - 5b + 6)

nhớ tik mik nha. Ak có j ko hiểu thì cứ bình luận ở dưới mik giải cho

a, \(7x^2+6x-13\)

=\(7x^2-7x+13x-13\)

=\(\left(7x^2-7x\right)+\left(13x-13\right)\)

=\(7x\left(x-1\right)+13\left(x-1\right)\)

=\(\left(x-1\right)\left(7x+13\right)\)

b, \(15\left(x-y\right)-25x+25y=15\left(x-y\right)-\left(25x-25y\right)\)

=\(15\left(x-y\right)-25\left(x-y\right)=\left(x-y\right)\left(15-25\right)\)

=(x-y).-10

b,36-(4a^2-20ab+25b^2)

=36-(2a-5b)^2

=(6-2a+5b)x(6+2a-5b)

a)\(36-4a^2+20ab-25b^2=6^2-\left(4a^2-20ab+25b^2\right)\)

\(=6^2-\left[\left(2a\right)^2-2.2a.5b+\left(5b\right)^2\right]\)

\(=6^2-\left(2a-5b\right)^2\)

\(=\left(6-2a+5b\right)\left(6+2a-5b\right)\)

b)\(a^3+3a^2+3a+1-27b^3=\left(a+1\right)^3-\left(3b\right)^3\)(chỗ này mình sửa 27b² thành 27b³ vì mình nghĩ nhầm đề)

\(=\left(a+1-3b\right)\left[\left(a+1\right)^2+\left(a+1\right)3b+\left(3b\right)^2\right]\)

\(=\left(a+1-3b\right)\left(a^2+2a+1+3ab+3b+9b^2\right)\)

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

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

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

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

a)  36-4a²+20ab-25b²

= 6^2 - (4a^2 - 20xb + 25b^2)

= 6^2 - (2a - 5b)^2

= [6 - (2a - 5b)] [6 + (2a - 5b)]

= (6 - 2a + 5b) (6 + 2a -5b)

a) \(6^2-\left(\left(2a\right)^2-2.2a.5b+\left(5b\right)^2\right)\)

\(=6^2-\left(2a-5b\right)^2\)

\(=\left(6-2a+5b\right)\left(6+2a-5b\right)\)

b) \(=\left(a+1\right)^3-\left(3b\right)^3\)

\(=\left(a+1-3b\right)\left(\left(a+1\right)^2+3b\left(a+1\right)+\left(3b\right)^2\right)\)

\(=\left(a+1-3b\right)\left(a^2+2a+1+3ab+3b+9b^2\right)\)

c) \(=\left(x+1\right)^3-3x\left(x+1\right)\)

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

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

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

Bài 1:

a) x³ - 3x² + 3x - 1 + 2(x² - x)

= (x - 1)³ + 2x(x - 1)

= (x - 1)[(x - 1)² + 2x]

= (x - 1)(x² - 2x + 1 + 2x)

= (x - 1)(x² + 1)

b) 36 - 4a² + 20ab - 25b²

= 36 - (2a - 5b)²

= (6 - 2a + 5b)(6 + 2a - 5b)

c) 5a³ - 10a²b + 5ab² - 10a + 10b

= 5(a³ - 2a²b + ab² - 2a + 2b)

= 5[a(a² - 2ab + b²) - 2(a - b)]

= 5[a(a - b)² - 2(a - b)]

= 5(a - b)(a² - ab - 2)

tích mình trước ik , mình sẽ giải qua tin nhắn  cho !

a) Số các số hạng trong A là: \(\left(25-1\right):1+1=25\) (số)

Tổng A bằng: \(\left(25+1\right)\cdot25:2=325\)

b) Số các số hạng trong B là: \(\left(50-2\right):2+1=25\) (số)

Tổng B bằng: \(\left(50+2\right)\cdot25:2=650\)

c) Số các số hạng trong C là: \(\left(81-1\right):4+1=21\) (số)

Tổng C bằng: \(\left(81+1\right)\cdot21:2=861\)

#Urushi

\(a,36-4a^2+20ab-25b^2\)

\(=6^2-\left(2a-5b\right)^2=\left(6-2a+5b\right)\left(6+2a-5b\right)\)\(b,x^2+2xy+y^2-xz-yz\)

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

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

\(d,5a^2-10a^2b+5ab^2-10a+10b\)

\(=5a^2-5a^2b-5a^2b+5ab^2-10a+10b\)

\(=5a\left(a-b\right)-5ab\left(a-b\right)-10\left(a-b\right)\)

\(=\left(a-b\right)\left(5a-5ab-10\right)\)