Question

[nood]

Giải các bất phương trình sau 

a) 4(x-3)²-(2x-1)²<10 

b) x(x-5)(x+5)-(x+2)(x²-2x+4)< hoặc = 3 

Answer 1

[YangSu]

\(a,4\left(x-3\right)^2-\left(2x-1\right)^2< 10\)

\(\Leftrightarrow4\left(x^2-6x+9\right)-\left(4x^2-4x+1\right)-10< 0\)
\(\Leftrightarrow4x^2-24x+36-4x^2+4x-1-10< 0\)

\(\Leftrightarrow-20x< -25\)

\(\Leftrightarrow x>\dfrac{5}{4}\)

\(b,x\left(x-5\right)\left(x+5\right)-\left(x+2\right)\left(x^2-2x+4\right)\le3\)

\(\Leftrightarrow x\left(x^2-25\right)-\left(x^3-2x^2+4x+2x^2-4x+8\right)\le3\)

\(\Leftrightarrow x^3-25x-\left(x^3+8\right)\le3\)

\(\Leftrightarrow x^3-25x-x^3-8-3\le0\)

\(\Leftrightarrow-25x\le11\)

\(\Leftrightarrow x\ge-\dfrac{11}{25}\)