Giải:
\(E=x^2-3x-15\)
\(\Leftrightarrow E=x^2-2.x.\dfrac{3}{2}+\left(\dfrac{3}{2}\right)^2-\dfrac{69}{4}\)
\(\Leftrightarrow E=\left(x-\dfrac{3}{2}\right)^2-\dfrac{69}{4}\ge-\dfrac{69}{4};\forall x\)
\(\Leftrightarrow E_{Min}=-\dfrac{69}{4}\)
\("="\Leftrightarrow x-\dfrac{3}{2}=0\Leftrightarrow x=\dfrac{3}{2}\)
Vậy ...
E= x2 - 3x -15
1, Tính a, Phép nhân 3x.( x2 - 3x + 2)
b, Phép chia (3x2 + x) : 3x
Cho 2 đa thức
P(x)= x2+5x4-3x2+x2+4x4+3x3-x+5
Q(x)=x-5x3-x2-x4+4x3-x2+3x-1
Tính P(x)+Q(x) ; P(x)-Q(x)
Tính a, Phép nhân 5x.( x2 - 2x + 1)
b, Phép chia (3x2 + x) : (-3x)
Tìm x biết :
a) 5/6 + (2/3x- -7/12) = 1/2
b) x/15 + 1,2 = 1/3
c) 7/1 - 5/18 = -3/2
d) 3 + | x-1,34 | = 5
e) 5-|x+2,56|=3
tìm x biết:
a, |2,7-x|=|-0,3|
b, 12/5 -|x+1,5|=0
c, 2. |2x-3|=1/3
d, 7,5-3.|5-2x|=-4/5
e, |3x-4|+|3y+15|=0
ê, |x-y|+ |y+9/25|=0
Cách hiểu 1:[TEX]\frac{44-x}{3}[/TEX]=[TEX]\frac{x-12}{5}[/TEX]
[TEX]\frac{220-5x}{15}[/TEX]=[TEX]\frac{3x-36}{15}[/TEX]
hay 220-5x=3x-36
=220-5x-3x+36=0
=220+36-5x-3x=0
=256-(5x+3x)=0
=256-8x=0
=8x=256
=x=32
tìm x biết
a.x:15=8:24
b.36:x=54:3
c.\(3^1_2:0,4=x:1^1_7\)
d.\(\frac{1}{5}x:3=\frac{2}{3}:0,25\)
e.\(\frac{3x+2}{5x+7}=\frac{3x-1}{5x+1}\)
f.\(\frac{x+1}{2x+1}=\frac{0,5x+2}{x+3}\)
gia tri cua x thoa man 2x+2/3x-6 = 2x-6/3x-15
