Câu a :

\(\left(x+2\right)\left(x+3\right)-\left(x-2\right)\left(x+5\right)=0\)

\(\Leftrightarrow x^2+3x+2x+6-x^2-5x+2x+10=0\)

\(\Leftrightarrow2x+16=0\)

\(\Rightarrow x=-8\)

Xem lại câu b .

Câu b chưa có ai làm!

b, \(3x\left(x-5\right)-\left(x-1\right)\left(2+3x\right)=0\)

\(\Rightarrow3x^2-15x-\left(2x+3x^2-2-3x\right)=0\)

\(\Rightarrow3x^2-15x+x-3x^2+2=0\)

\(\Rightarrow-14x=-2\Rightarrow x=\dfrac{1}{7}\)

Vậy..............................

Chúc bạn học tốt!!!

\(2x\left(12x-5\right)-8x\left(3x-1\right)=30\)

\(\Leftrightarrow24x^2-10x-24x^2+8x=30\)

\(\Leftrightarrow-2x=30\)

\(\Leftrightarrow x=-15\)

<br class="Apple-interchange-newline"><div></div>2x(12x−5)−8x(3x−1)=30

<=>\(24x^2-10x-24x^2+8x=30\)

<=>\(-2x=30\)

<=>\(x=30:\left(-2\right)\)

<=>\(x=-15\)

Bài làm :

\(2x\left(12x-5\right)-8x\left(3x-1\right)=30\)

\(\Leftrightarrow24x^2-10x-24x^2+8x=30\)

\(\Leftrightarrow-10x+8x=30\)

\(\Leftrightarrow-2x=30\)

\(\Leftrightarrow x=30:\left(-2\right)\)

\(\Leftrightarrow x=-15\)

Học tốt

Rảnh rỗi thật sự .-.

a)\(\Leftrightarrow3x^2-3x^2+6x=36\Leftrightarrow6x=36\Leftrightarrow x=6\)

a) \(\left(2x+3\right)\left(x-4\right)+\left(x+5\right)\left(x-2\right)=\left(3x-5\right)\left(x-4\right)\)

\(\Leftrightarrow2x^2-8x+3x-12+x^2-2x-5x+10=3x^2-12x-5x+20\)

\(\Leftrightarrow2x^2-8x+3x-12+x^2-2x+10=3x^2-12x+20\)

\(\Leftrightarrow3x^2-7x-2=3x^2-12x+20\)

\(\Leftrightarrow-7x+12x=20+2\)

\(\Leftrightarrow5x=22\)

\(\Rightarrow x=\dfrac{22}{5}\)

tick cho mk nha

b) \(\left(8x-3\right)\left(3x+2\right)-\left(4x+7\right)\left(x+4\right)=\left(2x+1\right)\left(5x-1\right)\)

\(\Leftrightarrow24x^2+16x-9x-6-4x^2-23x-28=10x^2+3x-1\)

\(\Leftrightarrow20x^2-16x-34-10x^2-3x+1=0\)

\(\Leftrightarrow10x^2-19x-33=0\)

\(\Delta=\left(-19\right)^2-4.10.\left(-33\right)=1320\)

\(x_1=3;x_2=\dfrac{-11}{10}\)

Tick cho mk nha

c) \(\left(3x-5\right)\left(7-5x\right)-\left(5x+2\right)\left(2-3x\right)=4\)

\(\Leftrightarrow21x-15x^2-35+25x-4x+15x^2-4=4\)

\(\Leftrightarrow42x-39=4\)

\(\Leftrightarrow42x=4+39\)

\(\Leftrightarrow42x=43\)

\(\Rightarrow x=\dfrac{43}{42}\)

Tick cho mk nha

Bạn coi lại đề giùm đi.

\(18x^2-6x-9x+3-18x^2+2x-27x+3=-6.\)

\(-15x+12+2x=0\)

\(-13x=-12\Leftrightarrow x=\frac{13}{12}\)

\(1+x-2\left(5+3x\right)=4-5x\)

\(1+x-10-6x=4-5x\)

\(x-6x+5x=4+10-1\)

\(0x=13\Leftrightarrow x=0\)

1) Ta có: \(1+x-2.\left(5+3x\right)=4-5x\)

        \(\Leftrightarrow1+x-10-6x=4-5x\)

        \(\Leftrightarrow x-6x+5x=4-1+10\)

        \(\Leftrightarrow0x=13\)( vô nghiệm )

Vậy \(S=\left\{\varnothing\right\}\)

\(1/1+x-2.\left(5+3x\right)=4-5x\)

\(=1+x-10-6x=4-5x\)

\(=>x+5x-6x=4+10-1=13\)

\(=>0=13\left(vl\right)\)

\(2/\left(2x-3\right)^3=-\left(-6^2\right)-\left(-2\right)^3+\left(-1\right)^{2011}\)

\(=>\left(2x-3\right)^3=36+8-1=43\)

(Lập phương của 1 hiệu: (a - b)³ = a³ - 3a²b + 3ab² - b³) sd hđt nhé :

=>2x³-3.2x².3-3.2x.3³-3³=43

=>2x³-2x².9-2x.81-27=43

đến đây thì dễ r 

a)\(9x^2+30x+25+9x^2-30x+25-\left(9x^2-2^2\right)\)

=\(9x^2+54\)=\(9\left(x^2+6\right)\)

b)\(2x\left(4x^2-4x+1\right)-3x\left(x^2-9\right)-4x\left(x^2+2x+1\right)\)

=\(8x^3-8x^2+2x-3x^3+27x-4x^3-8x^2-4x\)

=\(x^3-16x^2+25x\)

c)\(\left(x+y-z\right)^2-2\left(x+y-z\right)\left(x+y\right)+\left(x+y\right)^2\)

=\(\left(x+y-z-\left(x+y\right)\right)^2\)=\(\left(-z\right)^2\)

\(a,\left(3x+5\right)^2+\left(3x-5\right)^2-\left(3x+2\right)\left(3x-2\right)=9x^2+30x+25+9x^2-30x+25-9x^2+4=9x^2+54\)
\(b,BT=2x\left(4x^2-4x+1\right)-3x\left(x^2-9\right)-4x\left(x^2+2x+1\right)=8x^3-8x^2+2x-3x^3+27x-4x^3-8x^2-4x=x^3-16x^2+25x\)
\(c,BT=\left(x+y-z\right)^2-2\left(x+y-z\right)\left(x+y\right)+\left(x+y\right)^2=\left(x+y-z-x-y\right)^2=z^2\)