Problema Solution
the product of some negative number and 2 less than 2 times that number is 21. find the number
Answer provided by our tutors
let 'x' be the number and x<0
x*(2x-2) = 21
2x^2 - 2x - 21 = 0
by solving the quadratic equation we find the roots
x1 = - (43^0.5 - 1)/2
x2 = (43^0.5 + 1)/2
x1 = - 2.78
x2 = 3.78
since x<0 the solution is x = - 2.78.