a: \(\left(2x-3\right)\left(6x-4\right)-\left(3x+1\right)\left(5x-5\right)=31\)
\(\Leftrightarrow12x^2-8x-18x+12-\left(15x^2-15x+5x-5\right)=31\)
\(\Leftrightarrow12x^2-20x+12-15x^2+10x+5-31=0\)
\(\Leftrightarrow-3x^2-10x-14=0\)
\(\Leftrightarrow3x^2+10x+14=0\)
\(\text{Δ}=10^2-4\cdot3\cdot14=100-168=-68< 0\)
Do đó: Phương trình vô nghiệm
b: \(\left(2x-3\right)\left(4x-5\right)-\left(8x+1\right)\left(x-2\right)=12\)
\(\Leftrightarrow8x^2-10x-12x+15-\left(8x^2-16x+x-2\right)=12\)
\(\Leftrightarrow8x^2-22x+15-8x^2+15x+2=12\)
=>-7x+17=12
=>-7x=-5
hay x=5/7
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