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
b) Ta có: 5x-8=2x+7
\(\Leftrightarrow5x-2x=7+8\)
\(\Leftrightarrow3x=15\)
hay x=5
c) Ta có: \(4x^2+2x-5=4x^2-2x+3\)
\(\Leftrightarrow2x-5+2x-3=0\)
\(\Leftrightarrow4x=8\)
hay x=2
d) Ta có: \(2x^3-3x+6=2x^3+x\)
\(\Leftrightarrow-3x-x=-6\)
\(\Leftrightarrow4x=6\)
hay \(x=\dfrac{3}{2}\)
e) Ta có: \(2\left(x+4\right)-3\left(2x-5\right)=3\)
\(\Leftrightarrow2x+8-6x+15=3\)
\(\Leftrightarrow-4x=3-15-8=-20\)
hay x=5