While multiplying three real numbers, Ashok took one of the numbers as...
We know that one of the 3 numbers is 37.
Let the product of the other 2 numbers be x.
It has been given that 73x-37x = 720
36x = 720
x = 20
Product of 2 real numbers is 20.
We have to find the minimum possible value of the sum of the squares of the 2 numbers.
Let x=a*b
It has been given that a*b=20
The least possible sum for a given product is obtained when the numbers are as close to each other as possible.
Therefore, when a=b, the value of a and b will be √20.
Sum of the squares of the 2 numbers = 20 + 20 = 40.
Therefore, 40 is the correct answer.
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While multiplying three real numbers, Ashok took one of the numbers as...
Approach:
- Let the other two numbers be x and y.
- Initially, the product of the three numbers is xyz.
- After replacing one of the numbers with 73, the new product is (73)(xy) = 720 + xyz.
- Therefore, xyz - (73)(xy) = -720.
- We can factor this equation as follows: (x - 73)(y - 73)z = -720.
- Since x, y, and z are real numbers, we know that (x - 73)(y - 73) and z have the same sign.
- If (x - 73)(y - 73) and z are positive, then their product is positive, which means xyz - (73)(xy) > 0, which is a contradiction.
- Therefore, (x - 73)(y - 73) and z are negative.
- Since we want to minimize x^2 + y^2, we can assume without loss of generality that x <=>=>
- We can rewrite x^2 + y^2 as (x + y)^2 - 2xy.
- Let s = x + y and t = xy. Then we have s^2 - 2t = x^2 + y^2.
- We want to minimize s^2 - 2t subject to the constraint (x - 73)(y - 73)z = -720 and s = x + y.
- We can use Lagrange multipliers to solve this optimization problem.
Solution:
- Let L = s^2 - 2t + lambda[(x - 73)(y - 73)z + 720 - s].
- Taking partial derivatives with respect to s, t, x, y, and z, we get:
- ds/dt = -2, dt/ds = -1/2, dx/dt = -lambda(y - 73)z, dy/dt = -lambda(x - 73)z, dz/dt = -lambda(x - 73)(y - 73).
- Setting these equal to zero, we get:
- t = s/2,
- lambda = -2/s^2,
- (x - 73)(y - 73)z = -720/s + s,
- (x - 73)z = (y - 73)z,
- (y - 73)z = (x - 73)z.
- Solving these equations, we get:
- z = -720/[s(s - 146)],
- y = (73s - 720)/(s - 146),
- x = (73s + 720)/(s + 146).
- Since x <= y,="" we="">=>
- (73s + 720)/(s + 146) <= (73s="" -="" 720)/(s="" -="">=>
- 73s^2 - 720s - 105120 <= 73s^2="" +="" 720s="" -="">=>
- s^2 <=>=>
- Therefore, the minimum possible value of s^2 - 2t = x^2 + y^2 is (720/73) + 720/73 = 40.
- Hence
While multiplying three real numbers, Ashok took one of the numbers as...
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