rút gon
a, (x-2)(x+3)-(2x-1)2=?
b, (2a+3)2 -a(5a-2)=?
c, 3a(a-1)(a+2)-(3a+1)(1-3a) =?
các bạn giir hẳn ra giúp mk nhé
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
\(\left(7x-4\right)\left(2x+3\right)-13x\)
\(=14x^2+21x-8x-12-13x\)
\(=14x^2-12\)
\(a^3-\left(a^2-3a\right)\left(a+3\right)\)
\(=a^3-\left(a^3+3a^2-3a^2-9a\right)\)
\(=a^3-a^3-3a^2+3a^2+9a\)
\(=9a\)
\(\left(2a-b\right)\left(b+4a\right)+2a\left(b-3a\right)\)
\(=2ab+8a^2-b^2-4ab+2ab-6a^2\)
\(=\)\(2a^2-b^2\)
\(5b\left(2x-b\right)+\left(x-6a\right)\left(5a+2x\right)\)
\(=10bx-5b^2+5ax+2x^2-30a^2-12ax\)
\(=2x^2-30a^2-5b^2+10bx-7ax\)
1) \(ĐK:3-2a>0\Leftrightarrow a< \dfrac{3}{2}\)
2) \(ĐK:2x-5< 0\Leftrightarrow x< \dfrac{5}{2}\)
3) \(ĐK:3-5a< 0\Leftrightarrow a>\dfrac{3}{5}\)
4) \(ĐK:a< 0\)
5) \(ĐK:-a\ge0\Leftrightarrow a\le0\)
a)\(\left(x-2\right)\left(x+3\right)-\left(2x-1\right)^2\)
\(=x^2+x-6-\left(4x^2-4x+1\right)\)
\(=x^2+x-6-4x^2+4x-1\)
\(=5x-3x^2-7\)
b)\(\left(2a+3\right)^2-a\left(5a-2\right)\)
\(=4a^2+12a+9-5a^2+2a\)
\(=14a-a^2+9\)
c)\(3a\left(a-1\right)\left(a+2\right)-\left(3a+1\right)\left(1-3a\right)\)
\(=\left(3a^2-3a\right)\left(a+2\right)+9a^2-1\)
\(=3a^3+3a^2-6a+9a^2-1\)
\(=3a^3+12a^2-6a-1\)