Bài 1:Rút gọn:
a) A=\(\left|2.x+4,6\right|-2.x+15,4\)
b) B =\(\left|x+7,2\right|-\left|x-1,2\right|\)
c) C =8,5.x - 19,5 - \(\left|1,5.x+4,5\right|\)
d) D =8,5 + x - \(\left|8,5-x\right|\)
Bài 1:Rút gọn:
a) A=\(\left|2.x+4,6\right|-2.x+15,4\)
b) B =\(\left|x+7,2\right|-\left|x-1,2\right|\)
c) C =8,5.x - 19,5 - \(\left|1,5.x+4,5\right|\)
d) D =8,5 + x - \(\left|8,5-x\right|\)
Bài 1: Tính
\(N=\left(\dfrac{1}{4.9}+\dfrac{1}{9.14}+\dfrac{1}{14.19}+...+\dfrac{1}{44.49}\right).\dfrac{1-3-5-7-...-9}{89}\)
Bài 2 : Rút gọn
a) A = |2x + 4,6| - 2x + 15,4
b) B = |x + 7,2| - |x - 1,2|
c) C = 8,5x - 19, 5 - |1,5x + 4,5|
d) D = 8,5 + x - |8,5 - x|
Bài 3 : Tìm x và y \(\in\) N.Biết 25 - y2 = 8(x - 2009)2
Bài 4 ; Cho :
\(A=\left(\dfrac{1}{2^2}-1\right)\left(\dfrac{1}{3^2}-1\right)\left(\dfrac{1}{4^2}-1\right)...\left(\dfrac{1}{100^2}-1\right)\)
So sánh phân số sau vs \(\dfrac{-1}{2}\)
Bài 1 :
Sửa để : \(N=\left(\dfrac{1}{4.9}+\dfrac{1}{9.14}+\dfrac{1}{14.19}+....+\dfrac{1}{44.49}\right)\cdot\dfrac{1-3-5-7-..-49}{89}\)
\(N=\dfrac{1}{5}\cdot\left(\dfrac{1}{4}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{14}+\dfrac{1}{14}-\dfrac{1}{19}+...+\dfrac{1}{44}-\dfrac{1}{49}\right)\cdot\dfrac{1-\left(3+5+7+..+49\right)}{89}\)
\(N=\dfrac{1}{5}\cdot\left(\dfrac{1}{4}-\dfrac{1}{49}\right)\cdot\dfrac{1-624}{89}\)
\(N=\dfrac{1}{5}\cdot\dfrac{45}{196}\cdot\dfrac{-623}{89}\)
\(\Rightarrow N=\dfrac{9}{196}\cdot-7=\dfrac{-9}{28}\)
Bài 1 : Rút gọn
\(M=\dfrac{1^{2016}+2^{2016}+3^{2016}+...+10^{2016}}{2^{2016}+4^{2016}+6^{2016}+...+20^{2016}}\)
Bài 2 : Tính
\(N=\left(\dfrac{1}{4.9}+\dfrac{1}{9.14}+\dfrac{1}{14.19}+...+\dfrac{1}{44.49}\right).\dfrac{1-3-5-7-...-9}{89}\)
\(P=\dfrac{2^{12}.3^5-4^6.9^2}{\left(2^2.3\right)^6-8^4.3^5}-\dfrac{5^{10}.7^3-25^5.7^3-25^5.49^2}{\left(125.7\right)^3+5^9.14^3}\)
Bài 3: Rút gọn
a) A = |2x + 4,6| - 2x + 15,4
b) B = |x + 7,2| - |x - 1,2|
c) C = 8,5x - 19, 5 - |1,5x + 4,5|
d) D = 8,5 + x - |8,5 - x|
Bài 4 : Tìm x và y \(\in\) N.Biết 25 - y2 = 8(x - 2009)2
Bài 5 ; Cho :
\(A=\left(\dfrac{1}{2^2}-1\right)\left(\dfrac{1}{3^2}-1\right)\left(\dfrac{1}{4^2}-1\right)...\left(\dfrac{1}{100^2}-1\right)\)
So sánh phân số sau vs \(\dfrac{-1}{2}\)
Bài 2 : Rút gọn
a) A = |2x + 4,6| - 2x + 15,4
b) B = |x + 7,2| - |x - 1,2|
c) C = 8,5x - 19, 5 - |1,5x + 4,5|
d) D = 8,5 + x - |8,5 - x|
A=/2x+4,6/-2x+15,4
TH1:/2x+4,6/> hoặc =4,6
/2x+4,6/-2x+15,4
=(2x+4,6)-2x+15,4
=2x+4,6-2x+15,4
=2x+2x-4,6+15,4
=4x-20
Mình làm thế không biết đúng hay sai
Bài 3: Rút gọn
A= \(|2x+4,6|-2x+15,4\)
B= \(|x+7,2|-|x-1,2|\)
C= 8,5x -19,5 -\(|1,5x+4,5|\)
D= 8,5 + x - \(|8,5-x|\)
Bài 1: Tìm giá trị nhỏ nhất:
a) A=\(\left|x-\frac{5}{7}\right|+\frac{2}{3}\)
b) B=\(\left|5-x\right|-8,5\)
c) C=\(\left|x+\frac{1}{5}\right|-x+\frac{4}{7}\)
d) D=\(\left|x-2010\right|+\left|x-1975\right|\)
\(\left|x-\frac{5}{7}\right|\ge0\Rightarrow\left|x-\frac{5}{7}\right|+\frac{2}{3}\ge\frac{2}{3}\Rightarrow A_{min}=\frac{2}{3}.\text{Dâu "=" xay ra}\Leftrightarrow x=\frac{5}{7}\)
\(\left|5-x\right|\ge0\Rightarrow\left|5-x\right|-8,5\ge-8,5\Rightarrow B_{min}=-8,5.\text{ Dâu "=" xay ra}\Leftrightarrow x=5\)
\(\left(\frac{1}{4}x-1\right)+\left(\frac{5}{6}x-2\right)-\left(\frac{3}{8}x+1\right)=4,5
\)
=> \(\left(\frac{1}{4}x+\frac{5}{6}x-\frac{3}{8}x\right)-\left(1+2+1\right)=4,5\)
=>\(\frac{17}{24}x-4=4,5\)
=> \(\frac{17}{24}x=8,5\)
=> \(x=8,5:\frac{17}{24}\)
=> \(x=12\)
cho biểu thức sau: A\(\left(x-5\right)^2+\left(2x+1\right)^2-2\left(2x^2+8,5\right)\)
a) rút gọn biểu thúc a
b) tìm x để A=0
c)tìm x để A=36
a/ \(A=\left(x-5\right)^2+\left(2x+1\right)^2-2\left(2x^2+8,5\right)\)
\(=\left(x^2-2.x.5+5^2\right)+\left[\left(2x\right)^2+2.2x.1+1^2\right]-2.2x^2-2.8,5\)
\(=\left(x^2-10x+25\right)+\left(4x^2+4x+1\right)-4x^2-17\)
\(=x^2-10x+25+4x^2+4x+1-4x^2-17\)
\(=x^2-6x+9\)
\(=x^2-2.3x+3^2\)
\(=\left(x-3\right)^2\)
b/ A = 0
\(\Rightarrow\left(x-3\right)^2=0\)
\(\Rightarrow x-3=0\)
\(\Rightarrow x=0+3=3\)
c/ A = 36
\(\Rightarrow\left(x-3\right)^2=36\)
\(\Rightarrow\left(x-2\right)^2=\left(\pm6\right)^2\)
\(\Rightarrow\left[{}\begin{matrix}x-2=6\\x-2=-6\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=6+2=8\\x=-6+2=-4\end{matrix}\right.\)
Vậy................
Bài 1: Rút Gọn Biểu Thức
a, x(x-y)+(x+y)(x-y)
b, \(x\left(x-3\right)^2-x\left(x+5\right)\left(x+2\right)\))
c,\(\left(x+2\right)^2-\left(x-1\right)^2\)
d,\(2a\left(a-1\right)-2\left(a+1\right)^2\)