# Solve Each of the Following Systems of Equations by the Method of Cross-multiplication : Mx – My = M2 + N2 X + Y = 2m - Mathematics

Solve each of the following systems of equations by the method of cross-multiplication :

mx – my = m2 + n2

x + y = 2m

#### Solution

The given system of equations may be written as

mx - ny - (m^2 + n^2) = 0

x + y - 2m = 0

Here

a_1 = m, b_1 = -n, c_1 = -(n^2 + n^2)

a_2 = 1, b_2 = 1, c_2 = -2m

By cross multiplication, we have

x/(2mn + (m^2 + n^2)) = (-y)/(-2m^2 + (m^2 + n^2)) = 1/(m + n)

=> x/(2mn + m^2 + n^2) = (-y)/(-m^2 + n^2) = 1/(m + n)

=> x/(m + n)^2 = (-y)/(-m^2 + n^2) = 1/(m + n)

Now

x/(m + n)^2 = 1/(m + n)

=> x = (m + n^2)/(m + n)

=> x = m + n

And

(-y)/(-m^2 + n^2)  = 1/(m + n)

=> -y = (-m^2 + n^2)/(n + n)

=> y = (m^2 - n^2)/(m + n)

=> y = ((m - n)(m + n))/(m + n)`

=> y = m - n

Hence, x = m + n, y = m - n is the solution of the given system of equation.

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#### APPEARS IN

RD Sharma Class 10 Maths
Chapter 3 Pair of Linear Equations in Two Variables
Exercise 3.4 | Q 26 | Page 58