Toán Lớp 7: tìm x biết:315-x/101+313-x/103+309-x/107+4=0
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Toán Lớp 7: tìm x biết:315-x/101+313-x/103+309-x/107+4=0
Comments ( 2 )
*Giải đáp + giải thích các bước giải :
(315-x)/101 + (313-x)/103 + (311- x)/105 + (309-x)/107 + 4=0
=>((315-x)/101 + 1) + ((313-x)/103 + 1) +((311- x)/105 + 1) + ((309-x)/107 + 1) =0
=>((315-x)/101 + 101/101) + ((313-x)/103 + 103/103) + ((311- x)/105 + 105/105) +((309-x)/107 + 107/107) =0
=>(315-x+101)/101 + (313-x+103)/103 +(311-x+105)/105+ (309-x+107)/107 =0
=>((315+101)-x)/101 + ((313+103)-x)/103 + ((311+105)-x)/105 + ((309+107)-x)/107 =0
=>(416-x)/101 + (416-x)/103 + (416-x)/105 + (416-x)/107 =0
=>(416-x)*(1/101 + 1/103 + 1/105 + 1/107)=0
Do 1/101 + 1/103 + 1/105 + 1/107 \ne 0 .
=>416-x=0
=>x=416-0
=>x=416
Vậy x=416 .
#Blue
Giải đáp và lời giải
(315-x)/101+(313-x)/103+(311-x)/105+(309-x)/107+4=0
=>(315-x)/101+(313-x)/103+(311-x)/105+(309-x)/107=-4
=>((315-x)/101+1)+((313-x)/103+1)+((311-x)/105+1)+((309-x)/107+1)=-4+1+1+1+1
=>(416-x)/101+(416-x)/103+(416-x)/105+(416-x)/107=0
=>(416-x).(1/101+1/103+1/105+1/107)=0
=>416-x=0 (Vì 1/101+1/103+1/105+1/107\ne0)
=>x=416
Vậy x=416