Question

一元二次方程！5x²-18=9x，4x²-3x=52，5x²=4-2x

Answer 1

5x^2-18=9x
x^2-9x/5=18/5
(x-9/10)^2=18/5+81/100
(x-9/10)^2=441/100
x-9/10=21/10
x1=31/10
x-9/10=-21/10
x2=-6/5
所以原方程的解是：x1=31/10 x2=-6/5
4x^2-3x=52
x^2-3x/4=13
(x-3/8)^2=13+9/64
(x-3/8)^2=(29/8)^2
x-3/8=29/8
x1=4
x-3/8=-29/8
x2=-13/4
所以：原方程的解是：x1=4 x2=-13/4
5x^2=4-2x
x^2+2x/5=4/5
(x+1/5)^2=4/5+1/25
(x+1/5)^2=21/25
x+1/5=根号21/5
x1=根号21/5-1/5
x+1/5=-根号21/5
x2=-根号21/5-1/5
所以原方程的解是：
x1=根号21/5-1/5
x2=-根号21/5-1/5

Answer 2

5x²-18=9x
5x²-9x-18=0
(x-3)(5x+6)=0
1 -3
5 6
x=3或x=-6/5

4x²-3x=52
4x²-3x-52=0
1 -4
4 13
(x-4)(4x+13)=0
x=4或x=-13/4

5x²=4-2x
5x²+2x=4
(x²+2x/5 +1/25)=21/25
(x+1/5)²=21/25
x=(-1+√21)/5或x=(-1-√21)/5

Answer 3

5x²-18=9x
(5x+6)(x-3)=0
4x²-3x=52
(x-4)(4x+13)=0
5x²=4-2x
是无理根，套公式吧

Answer 4

5x²-18=9x，
5x²-9x-18=0
(5x+6)(x-3)=0
x=-6/5 或 x=3

4x²-3x=52，
4x²-3x-52=0
(4x+13)(x-4)=0
x=-13/4 或x=4

5x²=4-2x
5x²+2x-4=0
5(x-(-1+根号21)/5)(x-(-1-根号21)/5)=0
x=(-1+根号21)/5 或x=(-1-根号21)/5