解庆颤:
由14x+5-21x^2=-9
得念如14x-21x^2=-9-5,
即14x-21x^2=-14
因此誉高败3x^2-2x=2
6x^2-4x+5=(6x^2-4x)+5=2(3x^2-2x)+5=2×2+5=9
∵14x+5-21x²=-9
∴-21x²隐纳+14x=-9-5
即-21x²+14x=-14
即-7(3x²-2x)=-14
∴3x²郑缓-2x=2
∴6x²-4x+5=2(3x²-2x)+5
=4+5
=9
望采灶丛没纳
14x+5-21^2=-9
14x-21x^2=-14
2x-3x^2=-2
故3x^2-2x=2
6x^2-4x=4
所慎举以野孝胡颂拦6x^2-4x+5=9