1.5x^2-7x=242.6y^2-13y=-73.x^2=19x-904.4x^2+11x-14=05.3x^2+3=7x(第五小题用求根公式解）

Question

1.5x^2 - 7x =24
2.6y^2 - 13y = -7
3.x^2 = 19x - 90
4.4x^2 + 11x - 14 = 0
5.3x^2 + 3 = 7x (第五小题用求根公式解）

Answer 1

1. 5x^2 - 7x =24
5x^2 - 7x -24=0
(5x+8)(x-3)=0
x=-8/5 或 x=3
2" 6y^2 - 13y = -7
6y^2 - 13y +7=0
(6y-7)(y-1)=0
y=7/6,y=1
3: x^2 = 19x - 90
x^2 -19x + 90=0
(x-10)(x-9)=0
x=10, x=9
4:4x^2 + 11x - 14 = 0
x=[-11+√(11^2+4*4*14)]/(2*4) =(4√14-11)/8
x=[-11-√(11^2+4*4*14)]/(2*4) =(-4√14-11)/8
5:3x^2 + 3 = 7x
3x^2-7x+3=0
x=[7+√(7^2-4*3*3)]/(2*3) =(7+√13)/6
x=[7-√(7^2-4*3*3)]/(2*3) =(7-√13)/6