Solve the given system by substitution. r=5s r=1/2s-9

Question

r = −10; s = −2

r = 10; s = 2

r = 2; s = 10

r = −2; s = −10

a b c d

pls tell me which 1 a b c or d pls

Answer 1

I'd go with a) r=-10, s=-2,

still

the question is a little ambiguous

if it means

r=5s

r =1/2s -9

then

5s -1/2s = -9

10s^2 -1 = -18s

10s^2 +18s -1

s = -18/20 +/- (1/20)sqr(18^2 +40)

s = -9/10 +/-.05sqr364

s = about -.9 +/-.05(19) = about -.9+.95 or -.9-.95

s = about .05 or -1.85

r = about .25 or -9.25

(r,s) = (.25,.05) or (-9.25, -1.85) that 2nd option is close to a) -10,-2.

BUT the r=1/2s -9 might mean r= (1/2)s -9

or even r=1/(2s-9)

for r=(1/2)s -9 =5s

(9/2)s = -9

s = -9(2/9) = -2

r =5(-2) = -10

(r,s) = (-10,-2)

That came out with such a simple integer solution, this might be what was intended, especially since it matches answer a)

for r= 1/(2s-9), it looks more complicated

1/(2s-9)= 5s

5s(2s-9) = 1

10s^2 -45s -1 = 0

s = 45/20 +/-(1/20)sqr(45^ +40)

s= 225 +/-(.05)sqr2065

s= 225 +/-2.272

s = about 227.272 or 222.728

r = about 5s = 1136.36 or 1113.64

(r,s) = (1136.36, 227.272) or (1113.64, 222.728),

not even close to any of the 4 answers