\(A=\left(1-\dfrac{1}{2}\right)\left(1-\dfrac{1}{3}\right)..............\left(1-\dfrac{1}{n+1}\right)\)
\(=\left(\dfrac{2}{2}-\dfrac{1}{2}\right)\left(\dfrac{3}{3}-\dfrac{1}{3}\right)........\left(\dfrac{n+1}{n+1}-\dfrac{1}{n+1}\right)\)
\(=\dfrac{1}{2}.\dfrac{2}{3}..........\dfrac{n}{n+1}\)
\(=\dfrac{1}{n+1}\)
Các bạn ơi giúp mình vs T-T
1) A = \(\dfrac{15}{24}+\dfrac{7}{21}+\dfrac{9}{34}-1\dfrac{15}{17}+\dfrac{2}{3}\)
2) B = \(16\dfrac{2}{7}:\left(-\dfrac{3}{5}\right)-28\dfrac{2}{7}:\left(-\dfrac{3}{5}\right)\)
3) C = \(25.\left(-\dfrac{1}{3}\right)^3+\dfrac{1}{5}-2.\left(-\dfrac{1}{2}\right)^2-\dfrac{1}{2}\)
4) D = \(\left(-2\right)^3.\left(\dfrac{3}{4}-0,25\right):\left(2\dfrac{1}{4}-1\dfrac{1}{6}\right)\)
5) E = \(5\sqrt{6}-4\sqrt{9}+\sqrt{25}-0,3\sqrt{400}\)
Cho đa thức \(P\left(x\right)=ax^2+bx+c\). Trong đó \(a,b,c\) là các hằng số thỏa mãn \(\dfrac{a}{1}=\dfrac{b}{2}=\dfrac{c}{3}\) và \(a\ne0\). Tính \(\dfrac{P\left(-2\right)-3P\left(1\right)}{a}\).
Tính
\(\left(-0,75.\dfrac{-1}{4}\right):\left(-5\right)+\dfrac{1}{5}+\dfrac{1}{5}-\left(\dfrac{-1}{5}\right):\left(-3\right)\)
\(B=\dfrac{1}{2}+\left(\dfrac{1}{2}\right)^2+\left(\dfrac{1}{2}\right)^3+...+\left(\dfrac{1}{2}\right)^{98}+\left(\dfrac{1}{2}\right)^{99}\)
So sánh B với 1
Thực hiện phép tính:
\(A=\left(1-\dfrac{1}{1+2}\right).\left(1-\dfrac{1}{1+2+3}\right)...\left(1-\dfrac{1}{1+2+3+...+2016}\right)\)
\(a.\dfrac{2}{a}x^2y^3z\left(-x^3yz\right)\) (a,b là hằng số)
\(b.-ax\left(xy^3\right)\dfrac{1}{4}\left(-by\right)^3\) (a,b là hằng số)
a) \(\dfrac{11}{13}-\left(\dfrac{5}{42}-x\right)=\left(\dfrac{15}{28}-\dfrac{11}{13}\right)\)
b) \(\left(\dfrac{7}{2}-2x\right)x3\dfrac{2}{5}+1\dfrac{4}{5}=7\dfrac{6}{5}\)
c) \(\left|2x-\dfrac{1}{3}\right|=\dfrac{5}{3}-2\)
d) (2x-1)3= -27
e) \(\dfrac{16}{2x}=1\)
Thu gọn các đa thức sau,chỉ ra phần biến,phần hệ số,bậc của mỗi đơn thức thu được:
a) \(\left(-\dfrac{1}{3}x^2\right)\left(-24xy\right)4xy\)
b) \(\left(xy^2\right)\left(-2xy^3\right)\)
c) \(\dfrac{1}{5}x^2y^3z\left(\dfrac{1}{2}xyz\right)^3\)
d) \(\dfrac{1}{3}abxy\left(axy^2\right)^2\) (a,b là hằng số)
Cho hàm số \(f\left(x\right)=ax^3+bx^2+cx+d\) thỏa mãn \(f\left(-1\right)=2,f\left(0\right)=1,f\left(1\right)=7,f\left(\dfrac{1}{2}\right)=3\). Xác định giá trị \(a,b,c,d\).
