1,Tim x:
a) (x+3)2=(x+3)4
1)tim x biet rang:
a)3^x-1=1/243
b)2^x+2^x+3=144
c)81^-2x.27x=9^5
2)tim tiep so ghang thu 5 cua day so sau:-1/a^2;2/a^3;-6/a^4;24/a^5;...
3)tim so tu nhien x biet :
a)4^x+4^x+3=4160
b)2^x-1+5.2^x-2=7/32
a)tim GTNN cua
A=/x-2019/+(y-1)^2020-2
C=/x-3/+/x+4/-5
b)tim GTLN
B=3^2-4/x^2-25/
D=x-4/x-5
a, 1, Vì |x - 2019| ≥ 0 ; (y - 1)2020 ≥ 0 => |x - 2019| + (y - 1)2020 ≥ 0 => |x - 2019| + (y - 1)2020 + (-2) ≥ (-2) => A ≥ -2
Dấu " = " xảy ra <=> \(\hept{\begin{cases}x-2019=0\\y-1=0\end{cases}\Leftrightarrow}\hept{\begin{cases}x=2019\\y=1\end{cases}}\)
Vậy GTNN A = -2 khi x = 2019 và y = 1
2, Ta có: |x - 3| = |3 - x|
Vì |x - 3| + |x + 4| ≥ |x - 3 + x + 4| = |1| = 1
=> C ≥ 1 - 5 => C ≥ -4
Dấu " = " xảy ra <=> (3 - x)(x + 4) ≥ 0
+) Th1: \(\hept{\begin{cases}3-x\ge0\\x+4\ge0\end{cases}\Rightarrow}\hept{\begin{cases}x\le3\\x\ge-4\end{cases}\Rightarrow}-4\le x\le3\)
+) Th2: \(\hept{\begin{cases}3-x\le0\\x+4\le0\end{cases}\Rightarrow}\hept{\begin{cases}x\ge3\\x\le-4\end{cases}}\)(Vô lý)
Vậy GTNN của C = -4 khi -4 ≤ x ≤ 3
b,
1, Vì |x2 - 25| ≥ 0 => 4|x2 - 25| ≥ 0 => 32 - 4|x2 - 25| ≤ 32 = 9
Dấu " = " xảy ra <=> x2 - 25 = 0 <=> x2 = 25 <=> x = 5 hoặc x = -5
Vậy GTLN B = 9 khi x = 5 hoặc x = -5
2, Đk: x ≠ 5
\(D=\frac{x-4}{x-5}=\frac{\left(x-5\right)+1}{x-5}=1+\frac{1}{x-5}\)
Để D mang giá trị lớn nhất <=> \(\frac{1}{x-5}\)mang giá trị lớn nhất <=> x - 5 mang giá trị nhỏ nhất <=> x - 5 = 1 <=> x = 6
=> \(D=1+1=2\)
Vậy GTLN của D = 2 khi x = 6
bai 1:tim x(chu y dau * la dau nhan)
a)(x+1/4)+(3x-4)+2*(x-3)=1
b)2*(x-3)=3(x+2)-x+1
c)x*(x+3)+x(x-2)=2x*(x-1)
d)(x-1)*3x-2*(x+2)-2x=x(x-1)
a: \(\left(x+\dfrac{1}{4}\right)+\left(3x-4\right)+2\left(x-3\right)=1\)
=>\(x+\dfrac{1}{4}+3x-4+2x-6=1\)
=>\(6x-\dfrac{39}{4}=1\)
=>\(6x=1+\dfrac{39}{4}=\dfrac{43}{4}\)
=>\(x=\dfrac{43}{4}:6=\dfrac{43}{24}\)
b: \(2\left(x-3\right)=3\left(x+2\right)-x+1\)
=>\(2x-6=3x+6-x+1\)
=>2x-6=2x+7
=>-6=7(vô lý)
c: \(x\left(x+3\right)+x\left(x-2\right)=2x\left(x-1\right)\)
=>\(x^2+3x+x^2-2x=2x^2-2x\)
=>3x-2x=-2x
=>3x=0
=>x=0
d: \(\left(x-1\right)\cdot3x-2\left(x+2\right)-2x=x\left(x-1\right)\)
=>\(3x^2-3x-2x-4-2x=x^2-x\)
=>\(3x^2-7x-4-x^2+x=0\)
=>\(2x^2-6x-4=0\)
=>\(x^2-3x-2=0\)
=>\(x=\dfrac{3\pm\sqrt{17}}{2}\)
cho x^4-3*x^3+6*x^2-5*x+5=(x^2+a*x+1)*(x*2+b*x+3)
tim a+b=?
Tim x biet
A 3/2.x-2/5=1/3.x-1/4
B -51/2.x+1=3/4-7/6
C 2.x-2/3=7.x+3/2-1
D 3/2.x-2/5=1/3.x -1/4
a) \(\frac{3}{2}x-\frac{2}{5}=\frac{1}{3}x-\frac{1}{4}\)
\(\Rightarrow\frac{3}{2}x-\frac{1}{3}x=-\frac{1}{4}+\frac{2}{5}\)
\(\frac{7}{6}x=\frac{3}{20}\Rightarrow x=\frac{9}{70}\)
b) \(-5^{\frac{1}{2}x+1}=\frac{3}{4}-\frac{7}{6}\)
\(-5^{\frac{1}{2}x}.\left(-5\right)=-\frac{5}{12}\)
\(-5^{\frac{1}{2}x}=\frac{1}{12}\)
mà -51/2x mang giá trị âm
1/12 có giá trị dương
=> không tìm được x
c) \(\frac{2x-2}{3}=\frac{7x+3}{2-1}\)
\(\frac{2x-2}{3}=7x+3=\frac{21x+9}{3}\)
=> 2x - 2 = 21x + 9
=> 2x - 21x = 9 + 2
-19x = 11
x = -11/19
phần d bn lm như phần a nha
Tim X :
a)x:1/3+2/3[1/5-1] =4
b)1/2 [x-3/5]=-1/3[7/6-3/2]
c)1/3-3/4=3/5 -x
d)4/7x-2/3=1/3+x
a) x : 1/3 + 2/3[1/5 - 1] = 4
x : 1/3 + 2/3[1/5 - 5/5] = 4
x : 1/3 + 2/3 . -4/5 = 4
x : 1/3 + 2/3 = 4 : -4/5
x : 1/3 + 2/3 = 4 . -5/4
x : 1/3 + 2/3 = -5
x : 1/3 = -5 - 2/3
x : 1/3 = -15/3 - 2/3
x : 1/3 = -17/3
x = -17/3 . 1/3
x = -17/9
Các câu khác bn làm tương tự
Tim x, biet:
a)(x-3)^3-(x-3)(x^2+3x+9)+9(x-1)^2=15
b)(x^2-2)^2+4(x-1)^2-4(x^2-2)(x-1)=0
Giup minh voi!
a) Tinh gia tri bieu thuc:
3/5 : 4/5 + 1/2 x 2/3
b) Tim x:
5/4 nhan x = 3/8 + 1/4
A
\(\frac{3}{5}\div\frac{4}{5}+\frac{1}{2}\times\frac{2}{3}\)
\(=\frac{3}{4}+\frac{1}{3}\)
\(=\frac{13}{12}\)
B
\(\frac{5}{4}\times x=\frac{3}{8}+\frac{1}{4}\)
\(\frac{5}{4}\times x =\frac{5}{8}\)
\(x=\frac{5}{8}\div\frac{5}{4}\)
\(x=\frac{4}{8}=\frac{1}{2}\)
tim x :
a) |x+5|=1/7-|4/3-1/6|
b)|x+2/3|=1/2-[1/4-2/3]
c)|x-1/5|=|-5/2|-[1/4-2/3]
tim gtnn cua bt A
A= \((x-1)^4+(x-3)^4+6(x-1)^2\left(x-3\right)^2\)