Tractors

Two tractors plow the field in 4 hours together. If the first tractor plow 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 result:

a =  12 h
b =  6 h

Solution:

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=q±D2p=18±362 a1,2=18±62 a1,2=9±3 a1=12 a2=6   Factored form of the equation:  (a12)(a6)=0 a=a1=12=12 h

Our quadratic equation calculator calculates it.

b=18a=1812=6 h



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