Giúp em với ạ. Em camon
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Câu b
5x-8=2x+7
<=> 3x=7+8=15
<=>x=5
Câu c:
<=>4x=3+5
<=>4x=8
<=>x=2
Câu d
<=>6=4x
<=> x=3/2
Câu e
<=> 2x+8-6x+15=3
<=>4x=20
<=>x=5
b)5x-8=2x+7
⇔3x=15
⇔ x=5
c)4x2+2x-5=4x2-2x+3
⇔ 4x=8
⇔ x=2
d)2x3-3x+6=2x3+x
⇔ 4x=6
⇔ \(x=\dfrac{3}{2}\)
e)2(x+4)-3(2x-5)=3
⇔ 2x+4-6x+15=3
⇔ -4x+19=3
⇔ 4x=16
⇔ x=4
\(\Delta'=4-\left(m-1\right)=5-m\)
để pt có nghiệm kép khi \(5-m=0\Leftrightarrow m=5\)
chọn B
Phương trình có nghiệm kép khi:
\(\Delta'=4-\left(m-1\right)=0\Leftrightarrow5-m=0\)
\(\Rightarrow m=5\)
Ex6
1 was
2 had been
3 found
4 had talked
5 had spoken
6 snowed
7 were
8 painted
9 had
10 had known
Ex7
2 had got
3 had hurt
4 were
5 were
6 was
7 wanted
8 ?
9 stopped
10 had eaten
\(pt\text{⇔}\left(x^2+3x+2\right)\left(x+5\right)-x^3-8x^2-27=0\text{⇔}x^3+5x^2+3x^2+15x+2x+10-x^3-8x^2-27=0\\ \text{⇔}17x=17\text{⇔}x=1\)
Vậy nghiệm của phương trình : \(S=\left\{1\right\}\)
Ta có: \(\left(x+1\right)\left(x+2\right)\left(x+5\right)-x^3-8x^2=27\)
\(\Leftrightarrow\left(x^2+3x+2\right)\left(x+5\right)-x^3-8x^2=27\)
\(\Leftrightarrow x^3+5x^2+3x^2+15x+2x+10-x^3-8x^2=27\)
\(\Leftrightarrow17x=17\)
hay x=1
a: Ta có: \(\widehat{ABC}=\widehat{ACB}\)(ΔABC cân tại A)
\(\widehat{ACB}=\widehat{ECN}\)(hai góc đối đỉnh)
Do đó: \(\widehat{ABC}=\widehat{ECN}\)
Xét ΔMBD vuông tại D và ΔNCE vuông tại E có
BD=CE
\(\widehat{MBD}=\widehat{NCE}\)
Do đó: ΔMBD=ΔNCE
=>DM=EN
b: Ta có: DM\(\perp\)BC
EN\(\perp\)BC
Do đó: DM//EN
Xét ΔIDM vuông tại D và ΔIEN vuông tại E có
MD=EN
\(\widehat{MDI}=\widehat{ENC}\)(hai góc so le trong, DM//EN)
Do đó: ΔIDM=ΔIEN
=>IM=IN
=>I là trung điểm của MN
\(d,\left(2x-1\right)\left(x+3\right)+2x\left(2-x\right)=10-8\left(x+4\right)\\ \Leftrightarrow2x^2+6x-x-3+4x-2x^2=10-8x-32\\ \Leftrightarrow17x=19\Leftrightarrow x=\dfrac{19}{17}\)
vậy phương trình đã cho có nhiệm \(x=\dfrac{19}{17}\)
Ta có: \(\left(2x-1\right)\left(x+3\right)+2x\left(2-x\right)=10-8\left(x+4\right)\)
\(\Leftrightarrow2x^2+6x-x-3+4x-2x^2=-8x-22\)
\(\Leftrightarrow18x=-19\)
hay \(x=-\dfrac{19}{18}\)
1 has never met
2 are playing
3 Have you ever sung
4 has worked
5 will help
6 will wait
7 will phone
8 will pay
9 will stay
10 will invite
11 is studying
12 goes - is going
13 is raining - is sleeping
14 will be
1, has never met
2,are playing
3,Have-ever sung
4,has worked
5, will help
6,will wait
7,will phone
8,will pay
9,will stay
10 will invite
11is studying
12, goes, has gone
13,is raining
14, is sleeping
15, will be