作业帮 > 数学 > 作业

已知两个数的差为4,积为12,求这两个数

来源:学生作业帮 编辑:百度作业网作业帮 分类:数学作业 时间:2024/05/03 08:56:47
已知两个数的差为4,积为12,求这两个数
已知两个数的差为4,积为12,求这两个数
设这两个数分别是 a,b
a - b = 4
a b = 12
∴ (a - b)² = 16
a ² - 2 a b + b ² = 16
∵ a b = 12
∴ a ² - 2 × 12 + b ² = 16
a ² + b ² = 40
∴ a ² + 2 a b + b ² = 40 + 2 × 12 = 64
(a + b)² = 64
a + b = ± 8
① 当 a + b = 8 时,则:
∵ a - b = 4
∴ (a + b)+ (a - b)= 4 + 8 = 12
2 a = 12
a = 6
∴ b = 8 - a = 8 - 6 = 2
② 当 a + b = - 8 时,则:
∵ a - b = 4
∴ (a + b)+(a - b)= - 8 + 4 = - 4
2 a = - 4
a = - 2
∴ b = - 8 - a = - 8 -(- 2)= - 6
综上:① a = 6,b = 2, ② a = - 2,b = - 6