\(a,\left(x-3\right)\left(x+7\right)-\left(x+5\right)\left(x-1\right)=0\)
\(x^2-3x+7x-21-x^2-5x+x+5=0\)
\(-16=0\)
vậy pt vô nghiệm
\(b,\left(3x-1\right)\left(2x+7\right)-\left(x+1\right)\left(6x-5\right)=16\)
\(6x^2-2x+21x-7-6x^2-6x+5x+5=16\)
\(18x=18\)
\(x=1\left(TM\right)\)
Trả lời:
a, ( x - 3 ) ( x + 7 ) - ( x + 5 ) ( x - 1 ) = 0
<=> x2 + 7x - 3x - 21 - ( x2 - x + 5x - 5 ) = 0
<=> x2 + 7x - 3x - 21 - x2 + x - 5x + 5 = 0
<=> - 16 = 0 ( vô lí )
Vậy pt vô nghiệm.
b, ( 3x - 1 ) ( 2x + 7 ) - ( x + 1 ) ( 6x - 5 ) = 16
<=> 6x2 + 21x - 2x - 7 - ( 6x2 - 5x + 6x - 5 ) = 16
<=> 6x2 + 21x - 2x - 7 - 6x2 + 5x - 6x + 5 = 16
<=> 18x - 2 = 16
<=> 18x = 18
<=> x = 1
Vậy x = 1 là nghiệm của pt.
