Question

Tìm x, biết:

a) x(x+5).(x-5) - (x+2).(x²- 2x+4)=17

b) (3x-5).(7-5x) - (5x+2).(2-3x)=4

c) 6x² - (2x+5).(3x-2)=7

d) x(x-4) - (x²-8) = 0

Answer 1

a. \(x\left(x^2-25\right)-\left(x^3-2x^2+4x+2x^2-4x+8\right)=17\)

\(x^3-25x-\left(x^3+8\right)=17\)

\(x^3-25x-x^3-8=17\)

\(-25x=25\)

\(x=-1\)

Answer 2

c. \(6x^2-\left(6x^2-4x+15x-10\right)=7\)

\(6x^2-6x^2-11x+10=7\)

\(-11x=-3\)

\(x=\frac{3}{11}\)

Answer 3

d.\(x^2-4x-x^2+8=0\)

\(-4x=-8\)

\(x=2\)

Answer 4

b. \(21x-15x^2-35+25x-\left(10x-15x^2+4-6x\right)=4\)

\(-15x^2+46x-35-10x+15x^2-4+6x=4\)

\(42x-39=4\)

\(42x=42\)

\(x=1\)