Question
The product of two numbers is 21 and their sum is 10, what are the numbers
Answers
Reiny
If you are looking for whole numbers, I can think of only two numbers so that
3 x 7 = 21, and it so happens that 3+7 = 10
How easy was that?
3 x 7 = 21, and it so happens that 3+7 = 10
How easy was that?
Henry2,
Eq1: x * y = 21.In Eq1, replace X with
y = 21/x.
Eq2: x + y = 10.
In Eq2, replace Y with 21/x and solve for X:
x + 21/x = 10.
Multiply both sides by X:
x^2 + 21 = 10x,
x^2 - 10x + 21 = 0,
(x-3)(x- 7) = 0,
X = 3, or X = 7.
In Eq1, replace X with 3 and solve for Y:
3 + Y = 10,
Y = 7.
y
= 7.
y = 21/x.
Eq2: x + y = 10.
In Eq2, replace Y with 21/x and solve for X:
x + 21/x = 10.
Multiply both sides by X:
x^2 + 21 = 10x,
x^2 - 10x + 21 = 0,
(x-3)(x- 7) = 0,
X = 3, or X = 7.
In Eq1, replace X with 3 and solve for Y:
3 + Y = 10,
Y = 7.
y
= 7.
Henry2,
Note: The first line of my response should be Eq1: x * y = 21.