A little attempt to write Maths in English
(I know it is not a common topic when you learn a language, but I'm studying physics, so it's important for me to know how to write about maths properly in English. I would like to know if the text sounds natural as if it would be was real)
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In the next short article we will try to show how to get the expression for the root [singular] of a second-order linear equation using squares of first-order polynomials whose roots will be the roots of the second-order linear equation:
a*x^2 + b*x + c = 0 (I)
To avoid any kind of misunderstanding is we needed to explain what some of these expressions mean:
- 'alpha*beta' symbol means alpha times beta
- 'alpha/beta' means alpha divided by beta
- 'alpha^(beta)' means raise the number or expression of alpha to the power of beta, which could be a number or an algebraic expression
- 'sqrt(alpha)' means the square root of alpha.
Let be 'x_1' and 'x_2' be the two roots of the equation (I) whose variable is 'x'. We are trying to write the previous equation as the perfect square of the two first-order polynomials with roots 'x_1' and 'x_2':
(x-x_1)*(x-x_2) = 0 (II)
Now, we will multiply both sides of (I) by '4*a':
4*(a^2)*(x^2) + 4*a*b*x + 4*a*c = 0 (III)
Adding to both sides of (IV) 'b^2' we get: [the reader is in the present tense]
4*(a^2)*(x^2) + 4*a*b*x + 4*a*c + b^2 = b^2 (IV)
Moving '4*a*c' to the right side we have:
4*(a^2)*(x^2) + 4*a*b*x + b^2 = b^2 - 4*a*c (V)
Now, if we remember that a perfect square is:
(alpha + beta)^2 = alpha^2 + 2*alpha*beta + beta^2 (VI)
we see that the left side of (VI) is already a perfect square, so we can write (VI) as follows:
(2*a*x + b)^2 = b^2 - 4*a*c (VII)
Taking the square root to both sides of (VIII) we have two options:
2*a*x_1 + b = sqrt(b^2 - 4*a*c) => x_1 = (-b + sqrt(b^2 - 4*a*c))/(2*a) (VIII)
2*a*x_1 + b = - sqrt(b^2 - 4*a*c) => x_2 = (-b - sqrt(b^2 - 4*a*c))/(2*a) (IX)
And the problem is resolved [we can also just say "solved"], because we have already obtained the expression we were looking for.