bạn sử dụng 7 hằng đẳnng thức đó
a. A – B)3 = A3 – 3A2B + 3AB2 – B3
b. A2 – B2 = (A – B)(A + B)
c. (A + B)3 = A3 + 3A2B + 3AB2 + B3
d. A3 – B3 = (A – B)(A2 + AB + B2)
Giups e vs
bài 1 : tính :
a, \(\left(2x-\dfrac{1}{2}\right)^3\)
b \(\left(\dfrac{x}{2}-y\right)\left(\dfrac{x}{2}+y\right)\dfrac{ }{ }\)
c\(\left(x+\dfrac{1}{3}\right)^3\)
d\(\left(x-2\right)\left(x^2+2x+4\right)\)
Tìm x, biết:
a) \(\left(5x+1\right)^2=\dfrac{36}{49}\)
b) \(\left[\left(-0,5\right)^3\right]^x=\dfrac{1}{64}\)
c) \(2020^{\left(x-2\right).\left(2x+3\right)}=1\)
d) \(\left(x+1\right)^{x+10}=\left(x+1\right)^{x+4}\) với \(x\in Z\)
e) \(\dfrac{3}{4}\sqrt{x}-\dfrac{1}{2}=\dfrac{1}{3}\)
a)tìm các cặp số nguyên x;y thỏa mãn (2x-)(x+1)=|y+1|
b)\(\left|x+\dfrac{1}{1.3}\right|+\left|x+\dfrac{1}{3.5}\right|+\left|x+\dfrac{1}{5.7}\right|+...+\left|x+\dfrac{1}{97.99}\right|=50x\)
cho A=\(\left(\dfrac{1}{2^2}-1\right).\left(\dfrac{1}{3^2}-1\right).\left(\dfrac{1}{4^2}-1\right)...\left(\dfrac{1}{100^2}-1\right)\)hãy so sánh A với \(\dfrac{-1}{2}\)
Tìm x
a)\(\left(x+5\right)^3\)=-64
b)\(\left(2x-3\right)^2\)=9
c)\(\dfrac{x}{\dfrac{4}{2}}\)=\(\dfrac{4}{\dfrac{x}{2}}\)
d)\(\dfrac{-32}{\left(-2\right)^n}\)=4
e)\(\dfrac{8}{2x}=4\)
g)\(\left(\dfrac{1}{2}\right)^{2x-1}=\dfrac{1}{8}\)
h)\(\left(\dfrac{1}{2}\right)^2.x=\left(\dfrac{1}{2}\right)^5\)
i) \(\left(\dfrac{-1}{3}\right)x=\dfrac{1}{81}\)
Thu gọn các đơn thức :
a) \(\left(\dfrac{a}{2}\right)^33xy\left(4a^2x^3\right)\left(\dfrac{13}{3}ay^2\right)\)
b)\(\left(2x^2y^3z^4\right)^k\left(-\dfrac{1}{2}xy^2\right)^2\)
c) \(\left(\dfrac{7}{3}x^2y^3\right)^{10}\left(\dfrac{3}{7}x^5y^4\right)^{10}\)
Bài 1: Tìm x, biết :
a, \(\dfrac{11}{13}\) - \((\dfrac{5}{42}\) - x \()\) = - \((\)\(\dfrac{15}{28}\)- \(\dfrac{11}{15}\)\()\)
b, \(|x+\dfrac{4}{15}|\) - \(|-3,75|\)= - \(\left|-2,15\right|\)
c, \(\dfrac{5}{3}\) - \(\left|x-\dfrac{3}{2}\right|\) = \(\dfrac{-1}{2}\)
d,\(\left(x-\dfrac{2}{3}\right)\). \(\left(2x-\dfrac{3}{2}\right)\) = 0
BÀi 3: Tìm x,y biết
a, \(\left(x^2-4\right)^2\)+ \(\left(x+2^{ }\right)\)\(^2\) = 0
b, \(\left(x-y^{ }\right)^2\) + \(\left|y+2\right|\) = 0
c, \(\left|x-y\right|\)+ \(\left|y+\dfrac{9}{25}\right|\)= 0
d, \(\left|\dfrac{1}{2}-\dfrac{1}{3}+x\right|\)= \(\left(-\dfrac{1}{4}\right)\)- \(\left|y\right|\)
Tìm x biết:
a) \(\dfrac{-32}{\left(-2\right)^x}=4\) f) \(\left(3x-1\right)^3=\dfrac{-8}{27}\)
b) \(\left(\dfrac{1}{2}\right)^{2x-1}=\dfrac{1}{8}\) g) \(\left(2x+3\right)^2=\dfrac{9}{121}\)
c) \(\dfrac{1}{9}.27^x=3^x\) h) \(5^x+5^{x+2}=650\)
d) \(9^x:3^3=\dfrac{1}{243}\) i) \(\left(x-7\right)^{x+1}-\left(x-7\right)=0\)
e) \(\dfrac{x7}{81}=27\) m) \(\left(\dfrac{-3}{4}\right)^{3x-1}=\dfrac{256}{81}\)
Tìm y biết:
a) 2y . (y - \(\dfrac{1}{7}\)) = 0
b) \(-\dfrac{2}{5}+\dfrac{2}{3}y+\dfrac{1}{6}y=\dfrac{-4}{15}\)
Tìm các số x thỏa mãn:
a) \(x.\left(x-\dfrac{4}{7}\right)>0\)
b)\(\left(x-\dfrac{2}{5}x^2\right)< 0\)
c)\(\left(x-\dfrac{2}{5}\right).\left(x+\dfrac{3}{7}\right)>0\)
d)\(\left(x-\dfrac{2}{5}\right).\left(x+\dfrac{3}{7}\right).\left(x+\dfrac{3}{4}\right)>0\)
(* dấu . là dấu nhân nha bạn ^-^)
Tìm các số nguyên x sao cho tích của 2 số hữu tỉ \(-\dfrac{3}{x-1};\dfrac{x-2}{2}\) là một số nguyên
Giải :
Ta có :
\(-\dfrac{3}{x-1}.\dfrac{x-2}{2}=\dfrac{-3\left(x-2\right)}{\left(x-1\right).2}=\dfrac{-3x+6}{2x-2}\)
\(\dfrac{-3x+6}{2x-2}\) là một số nguyên khi \(-3x+6⋮2x-2\)
\(\Leftrightarrow2\left(-3x+6\right)+3\left(2x-2\right)⋮2x-2\\ \Leftrightarrow-6x+12+6x-6⋮2x-2\\ \Leftrightarrow\left(-6x+6x\right)+\left(12-6\right)⋮2x-2\\ \Leftrightarrow6⋮2x-2\\ \Leftrightarrow2x-2\inƯ\left(6\right)=\left\{1;-1;2;-2;3;-3;6;-6\right\}\\ \Leftrightarrow2x\in\left\{3;1;4;0;5;-1;8;-4\right\}\\ \Leftrightarrow x\in\left\{2;0;4;-2\right\}\)
