[Toán 10]giúp đỡ

Y

yeu_dai_kho

truoc tien tinh delta de tim dieu kien de PT co nghiem x1x2=>delta>0
delta=16m^2+36(m-1)^2=52m^2-72m+36=(m.can52-36/can52)^2+144/13>0 voi moi m
PT<=>x1+x2=4m (minh cung ko nho chinh xac he thuc viet,co the nham o cong thuc do,ban xem lai ho nha)
x1.x2=-9(m-1)^2 (theo viet)
co x1-x2=4 <=>(x1-x2)^2=16<=>(x1+x2)^2-4x1.x2=16
thay he thuc viet vao rui tim nghiem la ok
Chú ý gõ dấu
 
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