Horns Of A Number

Level pending

In 1545 the Italian physician and mathematician Girolamo Cardano (1501-1576) attempting to find two numbers whose sum is 10 and whose product is 40. Let A and B be the two number.

Find the value of 10A + B^{2}.


The answer is 60.

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1 solution

Anurag Pandey
Aug 25, 2016

Let the two number be a , b . According to the question, a + b = 10 a + b = 10 and a b = 40 ab=40 .

We can this assume a quadratic equation whose roots are a and b . Using Vieta's formula, The quadratic formed will be ,

x 2 ( s u m o f r o o t s ) x + ( p r o d u c t o f r o o t s ) = 0 x^2 - (sum of roots ) x + (product of roots ) = 0

x 2 10 x + 40 = 0 x^2 - 10x + 40 =0

a and b are the roots of the equation and thus it must satisfy the equations , Hence we get ,

b 2 10 b + 40 = 0 b^2 -10b + 40 = 0

b 2 = 10 b 40 b^2 = 10b -40

Now we need to find the value of ,

K ( l e t ) = 10 a + b 2 = 10 a + 10 b 40 K(let) = 10a + b^2 = 10a + 10b - 40

So , K = 10 ( a + b ) 40 = 100 40 = 60 K = 10(a + b) - 40 = 100 - 40 = 60

K = 60 \boxed{K = 60 }

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