已知数字可以表示为x n ,其中“ x”称为“基”,而“ n”称为“指数” 。用简单的话来说,我们可以说指数的意义在于它表明了我们乘以基数的次数。有某些指数定律,这些定律将使计算更容易,更快。让我们看一下定律和示例,为了更好地理解,在所有示例中我们都将x设为5,x可以是任何数字。
Laws |
Examples |
---|---|
x0 = 1 | 50 = 1 |
x1 = x | 51 = 5 |
x-1 = 1 / x | 5-1 = 1 / 5 |
xa xb = x(a + b) | 54 53 = 5(4 + 3) = 57 |
xa / xb = x(a – b) | 56 / 52 = 5(6 – 2) = 54 |
(xa)b = x(a * b) | (53)4 = 5(3 * 4) = 512 |
(xy)a = xaya | (5 * 6)2 = 52 * 62 |
(x/y)a = xa/ya | (5/6)3 = 53/6 3 |
x-a = 1/xa | 5-4 = 1/54 |
让我们更详细地讨论每条法律
法律1
If we have any number as base and exponent of that base is 0 then answer will be 1 .
For Example:
20 = 1
30 =1
120 = 1
法2
If we have any number as base and exponent of that base is 1 the answer is base itself.
For Example:
71 = 7
211 = 21
151 = 15
法律3
If we have any number as base and exponent of that base is -1 then answer will be reciprocal of that base.
For Example:
8-1 = 1 / 8
15-1 = 1 / 15
27-1 = 1 / 27
法4
If we have to multiply two numbers with same base and different exponents then
xaxb = xa + b
x3x4 = (x * x * x) * (x * x * x * x)
= (x * x * x * x * x * x * x)
= x(3 + 4)
= x7
For Example:
2423 = 2(4 + 3)
= 27
7574 = 7(5 + 4)
= 79
(12)6(12)2 = 12(6 + 2)
= 128
法5
If we have to divide two numbers with same base and different exponents then
xa / xb = xa – b
x5 / x3 = (x * x * x * x * x) / (x * x * x)
= (x * x)= x(5 – 3)
= x2
For Example:
34 / 32 = 3(4 – 2)
= 32
58 / 53 = 5(8 – 3)
= 55
(13)7 / (13)5 = 13(7 – 5)
= 132
法6
(xa)b = xab
(x2) 3 = (x * x)3
= (x * x) (x * x) (x * x)
= (x * x * x * x * x * x) = x(2 * 3)
= (x)6
For Example:
(23)4 = 2(3 * 4)
= 212
(52)3 = 5(2 * 3)
= 56
(134)5 = (13)(4 * 5)
= 1320
法7
If we have two numbers to multiply with different base but same exponent then
(x * y)a = xaya
(x * y)4 = (xy) (xy) (xy) (xy)
= xyxyxyxy
= xxxxyyyy = x4y4
For Example:
(5 * 4)2 = 52 * 42
(7 * 3)4 = 74 * 34
(12 * 32)9 = 129 * 329
法8
If we have to divide two numbers with different base but same exponent then
(x / y)a = xa / y a
(x / y)3 = (x/y)(x/y)(x/y)
= (x * x * x) / (y * y * y)
= x3 / y3
For Example:
(2 / 3)4 = 24 / 34
(6 / 8)2 = 62 / 82
(15 / 27)8 = 158 / 278
法9
x-a = 1 / xa
For Example:
8 -2 = 1 / 8-2
7-3 = 1 / 73
15-6 = 1 / 156
使用指数表达标准形式的小数
什么是标准数字形式?
碰巧的是,我们遇到的数字很小,无法正确读写,因此,有一种更好的方法可以用标准形式描述这些小数字。
例子:
- 计算机芯片的直径为0.000003m = 3 * 10 -6 m
- 尘粒质量为0.000000000753千克= 7.53 * 10 -10千克
- 可见光(紫色)的最短可见波长的长度是0.0000004 m。 = 4.0 * 10 -7 m
这些数字非常小,因此我们将其转换为标准格式,让我们看一下步骤:
- 步骤一:将小数位移到右边,直到小数位的左边只有1(非零)位。
- 第二步:假设我们将小数点右移了n位,然后将剩余的数乘以10 -n 。
例子:
- 0.000000000753 = 7.53 * 10-10
- 0.0000004 = 4 * 10-7
- 0.0000000894 = 8.94 * 10-8
- 0.00000000052 = 5.2 * 10-10