Question

Which value of x satisfies both -9x + 4y = 8 and -3x − y = 4 given the same value of y?

Answer 1

-9x+4y=8 ------(equation. 1)

-3x-4=4. -------(equation 2)

(1) + (2)

-12x+3y=12

-4x+y=4

y=4+4x --------(3)

substitute y value in eq (1)

-9x+4(4+4x)=8

-9x+16+16x =8

7x+16=8

7x=-8

x=-8/7

therefore substitute x in eq (3)

y=4+4(-8/7)

y=4-32/7 = 28-32/7

y= -4/7

x=-8/7, y=-4/7.