Question

solve the following system of equation 15x+4y=61 4x+15y=72

Answer 1

15x + 4y = 61 ---(1)
4x + 15y = 72 ---(2)
Adding (1) and (2)
(15+4)x + (15+4)y = 61+72
=> 19(x+y) = 133 => x+y = 133/19 = 7--(3)
Subtracting (1) and (2)
(15-4)x + (4-15)y = 61-72
=> 11x - 11y = -11 => 11(x-y) = -11
= x-y = -11 --(4)
From (3) and (4)
x + y = 7
x - y = -11
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2x = -4
=> x = -2
=> y= 7-x = 7+2 = 9