a, (2y -1)^3-2y(2y-3)^2-6y(2y-2) b, tìm x (2x+5)(2x-7)-(-4x-3)^2=16 (8x^2+3)(8x^2-3)-(8x^2-1)^2=22

a, \((2y -1)^3-2y(2y-3)^2-6y(2y-2)\)

\(=8y^3-3.4y^2+3.2y-1-2y(4y^2-12y+9)-12y^2+12y\)

\(=8y^3-12y^2+6y-1-8y^3+24y^2-18y-12y^2+12y\)

\(=-1\)

b,\((2x+5)(2x-7)-(-4x-3)^2=16\)

\(\Leftrightarrow 4x^2-14x+10x-35-(16x^2+24x+9)=16\)

\(\Leftrightarrow 4x^2-14x+10x-35-16x^2-24x-9=16\)

\(\Leftrightarrow -12x^2-28x-60=0\)

\(\Leftrightarrow -12(x^2+2.\dfrac{7}{6}x+\dfrac{49}{36})-\dfrac{131}{3}<0\) \(\forall x\)

\(\Rightarrow \) pt vô nghiệm.

\((8x^2+3)(8x^2-3)-(8x^2-1)^2=22\)

\(\Leftrightarrow 64x^4-9-(64x^4-16x^2+1)=22\)

\(\Leftrightarrow 16x^2=32\)

\(\Leftrightarrow x^2=2\)

\(\Leftrightarrow x=\pm\sqrt2\)