Question

solve the equation by using the method of cross multiplication: x+y=7, 5x +12y=7

Answer 1

We have two equations as follows :-

1) x + y = 7

2) 5x + 12y = 7

Solving this by cross multiplication :-
First we have to convert the equations into the form of ax + by + c = 0

So,
The two equations are

1) x + y - 7 =0

2) 5x + 12y - 7 = 0

So,
We know the format of cross multiplication that :-


X = b1c2 - b2c1 / a1b2 - a2b1

And,
Y = c1a2 - c2a1 / a1b2 - a2b1


This has been obtaines from the basic formula only.
When we will equate the x one with the constant one and y one with the constant one we will get the same result which i have used.


X = 1*(-7) - 12*(-7) / 1*12 - 5*1
X = -7 + 84 / 12 - 5
X = 77 / 7
X = 11

Again , for obtaining y

Y = (-7)*5 - (-7)*1 / 1*12 - 5*1
Y = -35 + 7 / 12 - 5
Y = -28 / 7
Y = (-4)

Hence,
The answer is x = 11 and y = (-4)

Answer 2

hey here is your answer

x=11 y=-4