Question

求数学答案，

Answer 1

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(2)4x²+12x+9=81,4x²+12x+-72=0,
(4)(6)(8)

追答

(2)4x²+12x+9=81,4x²+12x+-72=0,x²+3x+-18=0,(x-3)(x+6)=0,x=3，x-=6

(4)2x²+3x=3,2x²+3x-3=0,x=[-b±√(b²-4ac]/2a=[-3±√(3²-4*2*(-3))]/(2*2)=(-3±√33)/4

(6)x(2x-5)=4x-10,2x²-5x-4x+10=0,2x²-9x+10=0,(2x-5)(x-4)=0,x=4,x=5/2

(2)4x²+12x+9=81,4x²+12x+-72=0,x²+3x+-18=0,(x-3)(x+6)=0,x=3，x=-6

(4)2x²+3x=3,2x²+3x-3=0,x=[-b±√(b²-4ac]/2a=[-3±√(3²-4*2*(-3))]/(2*2)=(-3±√33)/4

(6)x(2x-5)=4x-10,2x²-5x-4x+10=0,2x²-9x+10=0,(2x-5)(x-4)=0,x=4,x=5/2

(8)1-8x+16x²=2-8x,16x²-8x+1-2+8x=16x²-1=0,x²=1/16,x=±1/4

更正：
(2)4x²+12x+9=81,4x²+12x+-72=0,x²+3x+-18=0,(x-3)(x+6)=0,x=3，x=-6 错误已经更正

(4)2x²+3x=3,2x²+3x-3=0,x=[-b±√(b²-4ac]/2a=[-3±√(3²-4*2*(-3))]/(2*2)=(-3±√33)/4

(6)x(2x-5)=4x-10,2x²-5x-4x+10=0,2x²-9x+10=0,(2x-5)(x-2)=0,x=2,x=5/2 错误已经更正

(8)1-8x+16x²=2-8x,16x²-8x+1-2+8x=16x²-1=0,x²=1/16,x=±1/4