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bệnh HO...:))

1.A.more B.correct C.snorkel D.bore

2.A.god B.professor C.correct D.honor

3.A.enjoyed B.performed C.finished D.urged

1.A.every B.evening C.potato D.factory

2.A.produce B.money C.improve D.because

1.A.more B.correct C.snorkel D.bore

2.A.god B.professor C.correct D.honor

3.A.enjoyed B.performed C.finished D.urged

1.A.every B.evening C.potato D.factory

2.A.produce B.money C.improve D.because

\(\Leftrightarrow x\left(x+1\right)\left(x^2+x+1\right)-42=\left(x-2\right)\left(x+3\right)\left(x^2+x+7\right)\)

\(\Rightarrow x-2=0\)

\(\Rightarrow x=2\)

\(\Rightarrow x+3=0\)

\(\Rightarrow x=-3\)

\(\Rightarrow1^2-4\left(1.7\right)=-27\)(D là cái nàY)

=>D<0 ( pt ko có nghiệm thực

=>x=2 hoặc -3

Bước 1: \(\left(\frac{1}{3\times5}+\frac{1}{5\times7}+\frac{1}{7\times9}+...+\frac{1}{19\times21}\right)=\frac{1}{7}\)

Bước 2: \(x=\frac{9}{7}\div\frac{1}{7}=9\)