Question

1. Tính:

a/ 3x.(5x² - 2x - 1)

b/ (x² - 2xy + 3).(-xy)

c/ (2x² - 3xy + y²).(x+y)

2. Tìm x, biết:

a/ 6x.(5x + 3) + 3x.(1 - 10x)

b/ (3x - 3).(5 - 21x) + (7x + 4).(9x - 5) = 44

Làm ơn . . .

Answer 1

1/

a. \(3x\left(5x^2-2x-1\right)\)

\(=15x^3-6x^2-3x\)

b. \(\left(x^2-2xy+3\right)\left(-xy\right)\)

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

c. \(\left(2x^2-3xy+y^2\right)\left(x+y\right)\)

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

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

Answer 2

a) thiếu đề

b) \(\left(3x-3\right)\left(5-21x\right)+\left(7x+4\right)\left(9x-5\right)=44\)

\(15x-63x^2-15+63x+63x^2-35x+36x-20=44\)

\(79x-35=40\)

\(79x=75\)

\(x=\frac{75}{79}\)

Answer 3

Câu 2 b) nhầm đoạn cuối

sửa từ dòng 3

\(79x-35=44\)

\(79x=79\)

\(x=1\)