Question

If 2x – 10y = -1 and 5x + 6y = 4 are true equations, what would be the value
of 7x - 4y?

Answer 1

Explanation:

If the equations are true, they can be solved simultaneously.

Consider 2x-10y=-1 as Eq1 and 5x+6y=4 as Eq2

Multiplying Eq1 with 3 and Eq2 with 5 we get,

6x-30y=-3 -- Eq3 and 25x+30y=20 -- Eq4

Adding Eq3 and Eq4,

31x=17 Therefore, x=17/31

Plugin x=17/31 in Eq3,

6(17/31)-30y=-3 --- y=13/62

Plug In values of x and y in 7x-4y we get,

7(17/31)-4(13/62) = 3

So the value of 7x-4y = 3.