Question

tìm x

a. 5x(x-3)(x+3)-(2x-3)²-5(x+2)³+34x(x+2)=1

b.(x-2)³+6(x+1)²-(x-3)(x²+3x+9)=97

Answer 1

\(a,\rightarrow5x\left(x^2-9\right)-\left(4x^2-12x+9\right)-5\left(x^3+6x^2+12x+8\right)+34x^2+68x=1\\ \rightarrow5x^3-45x-4x^2+12x-9-5x^3-30x^2-60x-40+34x^2+68x=1\\ \rightarrow-25x-49=1\\ \rightarrow-25x=50\\ \rightarrow x=-2\)

\(b,\rightarrow\left(x^3-6x^2+12x-8\right)+6\left(x^2+2x+1\right)-\left(x^3-27\right)=97\\ \rightarrow x^3-6x^2+12x-8+6x^2+12x+6-x^3+27=97\\ \rightarrow24x+25=97\\ \rightarrow24x=72\\ \rightarrow x=3\)