Tìm x
3\(^{3x}\)+3\(^{3x+2}\)= 7290
Đố ai làm nhanh nè
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\(\left|3x-1\right|\le7\)
\(\Rightarrow-7\le3x-1\le7\Rightarrow-6\le3x\le8\Rightarrow-2\le x\le\frac{8}{3}\)
\(2x^3+3x^2+2x+3=0\)
\(\Leftrightarrow2x^3+2x+3x^2+3=0\)
\(\Leftrightarrow2x\left(x^2+1\right)+3\left(x^2+1\right)=0\)
\(\Leftrightarrow\left(2x+3\right)\left(x^2+1\right)=0\) vì \(x^2+1>0\) nên \(2x+3=0\Rightarrow x=-\frac{3}{2}\)
Bài 5:
a. 1 - 2y + y2
= (1 - y)2
b. (x + 1)2 - 25
= (x + 1)2 - 52
= (x + 1 - 5)(x + 1 + 5)
= (x - 4)(x + 6)
c. 1 - 4x2
= 12 - (2x)2
= (1 - 2x)(1 + 2x)
d. 8 - 27x3
= 23 - (3x)3
= (2 - 3x)(4 + 6x + 9x2)
e. (đề hơi khó hiểu ''x3'' !?)
g. x3 + 8y3
= (x + 2y)(x2 - 2xy + y2)
$=x^3-2x^5$
b) $(x^2+1)(5-x)$
$=5x^2-x^3+5-x$
$=-x^3+5x^2-x+5$
c) $(x-2)(x^2+3x-4)$$=x^3+3x^2-4x-2x^2-6x+8$
$=x^3+x^2-10x+8$
d) $(x-2)(x-x^2+4)$$=x^2-x^3+4x-2x+2x^2-8$
$=-x^3+3x^2+2x-8$
e) $(x^2-1)(x^2+2x)$$=x^4+2x^3-x^2-2x$
f) $(2x-1)(3x+2)(3-x)$Trước hết:
$(3x+2)(3-x)=9x+6-3x^2-2x$
$=-3x^2+7x+6$
Do đó:
$(2x-1)(-3x^2+7x+6)$
$=-6x^3+14x^2+12x+3x^2-7x-6$
$=-6x^3+17x^2+5x-6$
g) $(x+3)(x^2+3x-5)$
$=x^3+3x^2-5x+3x^2+9x-15$
$=x^3+6x^2+4x-15$
h) $(xy-2)(x^3-2x-6)$$=x^4y-2x^2y-6xy-2x^3+4x+12$
i) $(5x^3-x^2+2x-3)(4x^2-x+2)$$=20x^5-5x^4+10x^3-4x^4+x^3-2x^2+8x^3-2x^2+4x-12x^2+3x-6$
$=20x^5-9x^4+19x^3-16x^2+7x-6$
a: \(\Leftrightarrow x\left(x-5\right)\left(x+5\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=5\\x=-5\end{matrix}\right.\)
`P(x)=\(4x^2+x^3-2x+3-x-x^3+3x-2x^2\)
`= (x^3-x^3)+(4x^2-2x^2)+(-2x-x+3x)+3`
`= 2x^2+3`
`Q(x)=`\(3x^2-3x+2-x^3+2x-x^2\)
`= -x^3+(3x^2-x^2)+(-3x+2x)+2`
`= -x^3+2x^2-x+2`
`P(x)-Q(x)-R(x)=0`
`-> P(X)-Q(x)=R(x)`
`-> R(x)=P(x)-Q(x)`
`-> R(x)=(2x^2+3)-(-x^3+2x^2-x+2)`
`-> R(x)=2x^2+3+x^3-2x^2+x-2`
`= x^3+(2x^2-2x^2)+x+(3-2)`
`= x^3+x+1`
`@`\(\text{dn inactive.}\)
a: P(x)-Q(x)-R(x)=0
=>R(x)=P(x)-Q(x)
=2x^2+3+x^3-2x^2+x-2
=x^3+x+1
ngôlãmtân
\(3^{3x}+3^{3x+2}=7290\)
\(3^{3x}+3^{3x}.3^2=7290\)
\(3^{3x}.\left(1+3^2\right)=7290\)
\(3^{3x}.\left(1+9\right)=7290\)
\(3^{3x}.10=7290\)
\(3^{3x}=\frac{7290}{10}\)
\(3^{3x}=729\)
\(3^{3x}=3^6\)
\(\Rightarrow3x=6\)
\(\Rightarrow x=2\)
vậy \(x=2\)
P/S: đừng ai copy bài mình nhé
Tìm x
33x+33x+2= 7290
Bài này dễ mà, tự làm đi !