Question

Which ordered pair in the form (a, b) is a solution of this equation?

7a – 5b = 28


A.
(4, 0)

B.
(0, 4)

C.
(–2, –3)

D.
(–3, –2)

Answer 1

`A. \\ (4,0) \\ a=4 \\ b=0 \\ \Downarrow \\ 7 * 4-5 * 0 \stackrel{?}{=} 28 \\ 28-0 \stackrel{?}{=} 28 \\ 28\stackrel{?}{=} 28 \\ 28=28 \\ true`


`B. \\ (0,4) \\ a=0 \\ b=4 \\ \Downarrow \\ 7 * 0 - 5 * 4 \stackrel{?}{=} 28 \\ 0-20 \stackrel{?}{=} 28 \\ -20 \stackrel{?}{=} 28 \\ -20 \\ot= 28 \\ not \ true`


`C. \\ (-2,-3) \\ a=-2 \\ b=-3 \\ \Downarrow \\ 7 * (-2) - 5 * (-3) \stackrel{?}{=} 28 \\ -14+15 \stackrel{?}{=} 28 \\ 1 \stackrel{?}{=} 28 \\ 1 \\ot= 28 \\ not \ true`


`D. \\ (-3,-2) \\ a=-3 \\ b=-2 \\ \Downarrow \\ 7 * (-3) -5 * (-2) \stackrel{?}{=} 28 \\ -21 +10 \stackrel{?}{=} 28 \\ -11 \stackrel{?}{=} 28 \\ -11 \\ot= 28 \\ not \ true`

The answer is A.