Đáp án:
Giải thích các bước giải:
$a)(2x-\frac{1}{3y})^2-(4x^2+2)_{}$
⇔ $(\frac{6xy-1}{3y})^2-4x^2-2_{}$
⇔ $\frac{(6xy-1)^2}{9y^2}-4x^2-2_{}$
⇔ $\frac{36x^2y^2-12xy+1}{9y^2}-4x^2-2_{}$
⇔ $\frac{36x^2y^2-12xy+1-36x^2y^2-18y^2}{9y^2}_{}$
⇔ $\frac{-12xy+1-18y^2}{9y^2}_{}$
$b)(x+4)(x-4)-(x+6)^2_{}$
⇔ $x^2-16-(x^2+12x+36)_{}$
⇔ $x^2-16-x^2-12x-36_{}$
⇔ $-12x-52_{}$
$c)(3x-1)(x+2)-3(x-5)(x+5)_{}$
⇔ $3x^2+6x-x-2-3x^2+75_{}$
⇔ $5x+73_{}$
$d)(2x+1)(1-2x)+4x(x-3)_{}$
⇔ $(1+2x)(1-2x)+4x^2-12x_{}$
⇔ $1-4x^2+4x^2-12x_{}$
⇔ $-12x+1_{}$
$e)2(3x-y)(3x+y)+(3x+y)^2+(3x-y)^2_{}$
⇔ $2.(9x^2-y^2)+9x^2+6xy+y^2+9x^2-6xy+y^2_{}$
⇔ $18x^2-2y^2+9x^2+6xy+y^2+9x^2-6xy+y^2_{}$
⇔ $36x^2_{}$
$f)(5x+2)^2+2(25x^2-4)+(5x-2)^2_{}$
⇔ $25x^2+20x+4+50x^2-8+25x^2-20x+4_{}$
⇔ $100x^2_{}$.
