a, \(\left(x-3\right)\left(x^2+3x+9\right)-x\left(x+4\right)\left(x-4\right)=5\)
\(\Rightarrow x^3+3x^2+9x-3x^2-9x-27-x\left(x^2-16\right)=5\)
\(\Rightarrow x^3-27-x^3-16x=5\)
\(\Rightarrow-16x-27=5\)
\(\Rightarrow-16x=32\Rightarrow x=-2\)
b, \(\left(x-2\right)^3-\left(x+5\right)\left(x^2-5x+25\right)+6x^2=11\)
\(\Rightarrow x^3-6x^2+12x-8-\left(x^3-5x^2+25x+5x^2-25x+125\right)+6x^2=11\)
\(\Rightarrow x^3-6x^2+12x-8-x^3-125+6x^2=11\)
\(\Rightarrow12x-133=11\Rightarrow12x=144\Rightarrow x=12\)
Chúc bạn học tốt!!!
a)
\(\left(x-3\right)\left(x^2+3x+9\right)-x\left(x+4\right)\left(x-4\right)=5\)
\(\Rightarrow x^3-3^3-x.\left(x^2-16\right)=5\)
\(\Rightarrow x^3-27-x^3+16.x=5\)
\(\Rightarrow16x-27=5\)
\(\Rightarrow16x=32\)
\(\Rightarrow x=2\)
Vậy x = 2
b)
\(\left(x-2\right)^3-\left(x+5\right)\left(x^2-5x+25\right)+6x^2=11\)
\(\Rightarrow x^3-6x^2+12x-8-x^3-125+6x^2=11\)
\(\Rightarrow12x-133=11\)
\(\Rightarrow12x=144\)
\(\Rightarrow x=12\)
Vậy x = 12
