Question

[Phạm Tuyết Ngân]

Bài 1.

a) Tìm x biết:  (x + 1)³ - (x + 3)².(x + 1) + 4x² = -12

b) C/m giá trị biểu thức sau không phụ thuộc vào biến: (x + 2).(x - 5) + 3.(x - 4).(x + 4) - (3x - 1/2)² + 5x²

Bài 2. 

a) Tính nhẩm: 54² + 46² + 92.54

b) Cho: x² + x + 1 = a

    Tính M= x⁴ + 2x³ + 5x² + 4x + 4 theo a

Answer 1

[Thợ Đào Mỏ Padda]

SORY I'M IN GRADE 6

Answer 2

[tieu yen tu]

bài 1: 

a,\(\left(x+1\right)^3-\left(x+3\right)^2\cdot\left(x+1\right)+4x^2=\)-12

\(\Rightarrow\left(x+1\right)\cdot[\left(x+1\right)^2-\left(x+3\right)^2]+4x^2=-12\)

\(\Rightarrow\left(x+1\right)\cdot[\left(x+1+x+3\right)\cdot\left(x+1-x-3\right)]+4x^2=-12\)

\(\Rightarrow\left(x+1\right)\cdot\left(2x+4\right)\cdot\left(-2\right)+4x^2=-4\cdot3\)

\(\Rightarrow\left(x+1\right)\cdot2\cdot\left(x+2\right)\cdot\left(-2\right)+4x^2=-4\cdot3\)

\(\Rightarrow\left(x+1\right)\cdot\left(x+2\right)\cdot\left(-4\right)+4x^2=-4\cdot3\)

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

\(\Rightarrow x^2+2x+x+2-x^2=3\)

\(\Rightarrow3x=1\Rightarrow x=\frac{1}{3}\)