Question

用开平方法解下列方程:

1.x^2=2.25
2.4x^2=3
3.7x^2-56=0
4.2(x-7)^2=14

Answer 1

1.x^2=2.25
解：x1=1.5
x2=-1.5

2.4x^2=3
解:(2x)²=3
2x=正负3
x1=3/2 x2=-3/x
3.7x^2-56=0
解: 7x²=56
x²=8
x1=2个根号2
x2=负2个根号2

4.2(x-7)^2=14
解： (x-7)²=7
x-7=正负根号7
x1=根号7 +7
x2=-根号7 +7

Answer 2

1.x^2=2.25
x=±1.5
x1=1.5 x2=-1.5
2.4x^2=3
x^2=3/4
x=±(√3)/2
x1=(√3)/2 x2=-(√3)/2
3.7x^2-56=0
7x^2=56
x^2=8
x=±（2√2）
x1=2√2 x2=-2√2
4.2(x-7)^2=14
(x-7)^2=7
x-7=±√7
x1=7+√7 x2=7-√7

Answer 3

解1：x^2=2.25
x^2=(±1.5)^2
x=±1.5

解2：4x^2=3
x^2=3/4
x^2=[(±√3)/2]^2
x=±(√3)/2

解3：7x^2-56=0
7x^2=56
x^2=8
x^2=(±2√2)^2
x=±(√2)/2

解4：2(x-7)^2=14
(x-7)^2=7
(x-7)^2=(±√7)^2
x-7=±√7
x=7±√7

Answer 4

1.x^2=2.25
X=(+-1.5)^2
X1=1.5,X2=-1.5
2.4x^2=3
X^2=3/4
X1=√3/2 X2==√3/2
3.7x^2-56=0
x^2=56/7=8
X1=2√3, X2=-2√3
4.2(x-7)^2=14
(x-7)^2=7
(x-7)1=√7 (x-7)2=-√7
X1=7+√7 X2=7-√7