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}.
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Let the two number be a , b . According to the question, a + b = 1 0 and a b = 4 0 .
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 − 1 0 x + 4 0 = 0
a and b are the roots of the equation and thus it must satisfy the equations , Hence we get ,
b 2 − 1 0 b + 4 0 = 0
b 2 = 1 0 b − 4 0
Now we need to find the value of ,
K ( l e t ) = 1 0 a + b 2 = 1 0 a + 1 0 b − 4 0
So , K = 1 0 ( a + b ) − 4 0 = 1 0 0 − 4 0 = 6 0
K = 6 0