11A
12C
13D
14A
15D
16D
17B
18A
19D
20A
Câu 20: \(A=\left(2x+3\right)\left(4-6x\right)=8x-12x^2+12-18x=-12x^2-10x+12\)
=>Chọn A
Câu 19:
\(A=\left(x+3\right)\left(9x-8\right)=\left(0+3\right)\left(9\cdot0-8\right)=-24\)
=>Chọn D
Câu 18: \(A=\left(2x-3\right)\left(6x+4\right)=\left(2\cdot1-3\right)\left(6\cdot1+4\right)=10\cdot\left(-1\right)=-10\)
=>Chọn A
Câu 17: \(\left(x+2\right)\left(x+5\right)=x^2+7x+10\)
=>Chọn B
Câu 16:
\(\left(4x-5\right)\left(2x+3\right)=\left(4\cdot0-5\right)\left(2\cdot0+3\right)=-5\cdot3=-15\)
=>Chọn D
Câu 15: \(A=\left(x^3-2x^2+x-1\right)\left(5x^3-x\right)=\left(0-2\cdot0+0-1\right)\left(5\cdot0^3-0\right)=0\)
=>Chọn D
Câu 14: \(\left(3x-2\right)\left(x-2\right)=\left(3\cdot1-2\right)\left(1-2\right)=\left(3-2\right)\left(-1\right)=-1\)
=>Chọn A
Câu 13: \(\left(12x-5\right)\left(4x-1\right)=\left(12\cdot0-5\right)\left(4\cdot0-1\right)=5\)
=>Chọn D
Câu 12: \(x^2\left(3x^3-2x-1\right)=3x^5-2x^3-x^2\)
=>Chọn C
Câu 11: \(\left(x-2\right)\left(x-5\right)=x^2-5x-2x+10=x^2-7x+10\)
=>Chọn A
