Tractors

Two tractors plow the field for 4 hours together. If the first tractor plowed half of the field and then the second tractor completed the job, it would take 9 hours. How many hours does the field plow for each tractor separately?

Correct answer:

a =  12 h
b =  6 h

Step-by-step explanation:

4 (1/a+1/b) = 1  a/2 + b/2 = 9 a + b = 18 b = 18a  4 (b+a)=ab=0 4 ((18a)+a)=a(18a)  4 ((18a)+a)=a(18a) a218a+72=0  p=1;q=18;r=72 D=q24pr=1824172=36 D>0  a1,2=2pq±D=218±36 a1,2=218±6 a1,2=9±3 a1=12 a2=6 a=a1=12=12 h

Our quadratic equation calculator calculates it.

b=18a=1812=6 h



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