x = -30 ; y = -70 thì
A : l x l <
B : l x l > l y l
C : x < y
D : cả A ,B ,C đều đúng
Kích thước hố loại 2 làm đất trồng cây (chiều dài x chiều rộng x chiều sâu) là: A. 30 x 30 x 30 cm B. 30 x 40 x 30 cm C. 40 x 40 x 40 cm D. 40 x 40 x 30 cm
Chọn các đáp án đúng:
(600 : 30) : 5 = 600 : (30 : 5)
(600 + 30) + 5 = 600 + (30 + 5)
(600 - 30) - 5 = 600 - (30 - 5)
(600 x 30) x 5 = 600 x (30 x 5)
Các đáp án nha.
Đáp án đúng là:
(600 + 30) + 5 = 600 + (30 + 5)
(600 x30) x 5 = 600 x ( 30 x 5)
(600 x 30) x 5 = 600 x (30 x 5)
(600 + 30) + 5 = 600 +(30 + 5)
30 x 2 + 30 x 5 + 30 x 3
30 x 2 + 30 x 5 + 30 x 3
= 30 x ( 2 + 5 + 3 )
= 30 x 10
= 300
30 x 2+ 30 x 5 +30 x3
30x[2+5+3]
30x 10
300
30 + 30 x 20 + 30 x 10 = ?
30 + 30 * 20 + 30 * 10
= 30 * 1 + 30 * 20 + 30 * 10
= 30 * ( 1 + 20 + 10 )
= 30 * 31
= 930
30 + 30 x20 + 30 x 10
= 30 x 1 + 30 x 20 + 30 x 10
= 30 x ( 1 + 20 + 10 )
= 30 x 31
= 930
****nha
30 + 30 * 20 + 30 * 10
= 30 * 1 + 30 * 20 + 30 * 10
= 30 * ( 1 + 20 + 10 )
= 30 * 31
= 930
Tìm X: \(\dfrac{30-x}{30}=\dfrac{8}{15};\dfrac{x+30}{72}=\dfrac{5}{8}\)
\(\dfrac{30-x}{30}=\dfrac{8}{15}\)
\(\Rightarrow\left(30-x\right)15=30\times8\)
\(\Rightarrow\left(30-x\right)15=240\)
\(\Rightarrow30-x=240:15\)
\(\Rightarrow30-x=16\)
\(\Rightarrow x=30-16\)
\(\Rightarrow x=14\)
__
\(\dfrac{x+30}{72}=\dfrac{5}{8}\)
\(\Rightarrow\left(x+30\right)8=5\times72\)
\(\Rightarrow\left(x+30\right)8=360\)
\(\Rightarrow x+30=360:8\)
\(\Rightarrow x+30=45\)
\(\Rightarrow x=45-30\)
\(\Rightarrow x=15\)
5 + 5 x 6 - 30 + 30 x 30 =
5+5*6-30+30*30
=5+30-30+900
=905
5 + 5 x 6 - 30 + 30 x 30 = 5 + 30 - 30 + 900 = 905
30+30-30+30 x 30
a. x(x-1)(x+1)(x+2)=24
b.\(\dfrac{1}{x^2-5x+6}+\dfrac{1}{x^2-7x+12}+\dfrac{1}{x^2-9x+20}+\dfrac{1}{x^2-11x+30}=\dfrac{1}{8}\)
c.\(\dfrac{x-29}{30}+\dfrac{x-30}{29}=\dfrac{29}{x-30}+\dfrac{30}{x-29}\)
a.
\(x\left(x-1\right)\left(x+1\right)\left(x+2\right)=24\)
\(\Leftrightarrow x\left(x+1\right).\left(x-1\right)\left(x+2\right)-24=0\)
\(\Leftrightarrow\left(x^2+x\right)\left(x^2+x-2\right)-24=0\)
Đặt \(a=x^2+x-1\) , ta có pt:
\(\left(a+1\right)\left(a-1\right)-24=0\)
\(\Leftrightarrow a^2-1-24=0\)
\(\Leftrightarrow a^2-25=0\)
\(\Leftrightarrow\left(a-5\right)\left(a+5\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}a=5\\a=-5\end{matrix}\right.\)
*Với a = 5 ta được:
\(x^2+x-1=5\)
\(\Leftrightarrow x^2+x-6=0\)
\(\Leftrightarrow x^2+3x-2x-6=0\)
\(\Leftrightarrow\left(x^2+3x\right)-\left(2x+6\right)=0\)
\(\Leftrightarrow x\left(x+3\right)-2\left(x+3\right)=0\)
\(\Leftrightarrow\left(x+3\right)\left(x-2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-3\\x=2\end{matrix}\right.\)
*Với a = -5 ta được:
\(x^2+x-1=-5\)
\(\Leftrightarrow x^2+x+4=0\)
\(\Leftrightarrow x^2+2.x.\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{15}{4}=0\)
\(\Leftrightarrow\left(x+\dfrac{1}{2}\right)^2+\dfrac{15}{4}=0\) ( loại)
Vậy pt có tập nghiệm là: \(s=\left\{-3;2\right\}\)
c)(ĐKXĐ: x khác 30;29)
\(\Leftrightarrow\dfrac{x-29}{30}-1+\dfrac{x-30}{29}-1=\dfrac{29}{x-30}-1+\dfrac{30}{x-29}-1\)
\(\Leftrightarrow\dfrac{x-59}{30}+\dfrac{x-59}{29}=\dfrac{x-59}{30-x}+\dfrac{x-59}{29-x}\)
\(\Leftrightarrow x=59\)(tm) or \(\dfrac{1}{30}+\dfrac{1}{29}-\dfrac{1}{30-x}-\dfrac{1}{29-x}=0\)
\(\Leftrightarrow\dfrac{-x}{30\left(30-x\right)}+\dfrac{-x}{29\left(29-x\right)}=0\)
\(\Leftrightarrow x=0\)(tm) or \(\dfrac{1}{30\left(30-x\right)}+\dfrac{1}{29\left(29-x\right)}=0\)
\(\Leftrightarrow1741-59x=0\)
\(\Leftrightarrow x=\dfrac{1741}{59}\left(tm\right)\)
Vậy S={0;\(\dfrac{1741}{59}\);59}
b)(ĐKXĐ:x khác 2;3;4;5;6)
\(\Leftrightarrow\dfrac{1}{\left(x-2\right)\left(x-3\right)}+\dfrac{1}{\left(x-3\right)\left(x-4\right)}+\dfrac{1}{\left(x-4\right)\left(x-5\right)}+\dfrac{1}{\left(x-5\right)\left(x-6\right)}=\dfrac{1}{8}\)
\(\Leftrightarrow\dfrac{1}{x-3}-\dfrac{1}{x-2}+\dfrac{1}{x-4}-\dfrac{1}{x-3}+\dfrac{1}{x-5}-\dfrac{1}{x-4}+\dfrac{1}{x-6}-\dfrac{1}{x-5}=\dfrac{1}{8}\)
\(\Leftrightarrow\dfrac{1}{x-6}-\dfrac{1}{x-2}=\dfrac{1}{8}\)
\(\Leftrightarrow\dfrac{4}{\left(x-6\right)\left(x-2\right)}=\dfrac{1}{8}\)
\(\Leftrightarrow x^2-8x+12=32\)
\(\Leftrightarrow x^2-8x-20=0\)
\(\Leftrightarrow\left(x+2\right)\left(x-10\right)=0\)
\(\Leftrightarrow x=-2\) or x=10(đều thỏa)
Vậy ...
15: nếu \(\dfrac{x}{-15}\)=\(\dfrac{-60}{x}\) thì kết quả x bằng:
A) x=30 B) x=30 hoặc x=-1 C) x=3= hoặc x=-30 D) x=\(\dfrac{60}{15}\)
\(x^2=900\Leftrightarrow x^2=30^2\Rightarrow x=30\)
Chọn A
Tính A=(\(\sqrt{x-\sqrt{30}}-\sqrt{x+\sqrt{30}}\))\(\sqrt{x+\sqrt{x^2-30}}\)với x lớn hơn hoặc bằng \(\sqrt{30}\)