3x5^2-27:3^2+5^2x4-18:3^2
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3 . 52 - 27 : 32 + 52 . 4 - 18 : 32
= 3 . 25 - 27 : 9 + 25 . 4 - 18 : 9
= 75 - 3 + 100 - 2
= 170
a) \(3.5^2-27:3^2-5^2.4-18:3^2\)
\(=3.\left(5^2-5^2\right).27:\left(3^2-3^2\right)\)
\(=15.0.27.0\)
\(=0.0=0\)
b)
2x-1 là bội của x+3
=> 2x-1 chia hết cho x+3
hay [2(x+3)-7] chia hết ho x+ 3
=> 7 chia hết cho x+ 3
x+3 εεƯ(7)={1,-1,7,-7}
x+3=1 x+3=-1 x+3=7 x+3= -7
x = 1-3 x = -1-3 x = 7-3 x = -7-3
x = -2 x = -4 x =4 x = -10
Vậy x= -2, x=-4,x= 4, x= -10
c) \(205-\left[1200-\left(4^2-2.3\right)^3\right]:40\)
\(=205-\left[1200-16-6^3\right]:40\)
\(=205-\left[1200-10^3:40\right]\)
\(=205-1200-1000:40\)
\(=205-200:40\)
\(=205-5\)
\(=200\)
M=1/4(4/1*5+8/5*13+12/13*15+16/25*41)
=1/4(1-1/5+1/5-1/13+...+1/25-1/41)
=1/4*40/41=10/41
N=1/3(6/1*7+9/7*16+...+18/43*61)
=1/3(1-1/7+...+1/43-1/61)
=1/3*60/61=20/41
=>M<N
2/5= 0,4
3/4= 0,75
18/5= 3,6
mk nghĩ vậy ko chắc chắn đúng k nhé
\(\frac{2}{5}=\frac{2x2}{5x2}=\frac{4}{10}=0,4\)
\(\frac{3}{4}=\frac{3x25}{4x25}=\frac{75}{100}=0,75\)
\(\frac{18}{5}=\frac{18x2}{5x2}=\frac{36}{10}=3,6\)
Học tốt
2:
a: \(=\left(2x^2-xy\right)+\left(2xz-yz\right)\)
\(=x\left(2x-y\right)+z\left(x-2y\right)=\left(x-2y\right)\left(x+z\right)\)
b: \(=\left(x^2-4y^2\right)-\left(x-2y\right)\)
\(=\left(x-2y\right)\left(x+2y\right)-\left(x-2y\right)\)
\(=\left(x-2y\right)\left(x+2y-1\right)\)
c: \(=\left(y^2+10y+25\right)-9z^2\)
\(=\left(y+5\right)^2-\left(3z\right)^2\)
\(=\left(y+5+3z\right)\left(y+5-3z\right)\)
d: \(=\left(x+2y\right)^3-\left(x-2y\right)\left(x+2y\right)\)
\(=\left(x+2y\right)\left[\left(x+2y\right)^2-\left(x-2y\right)\right]\)
\(=\left(x+2y\right)\left(x^2+4xy+4y^2-x+2y\right)\)
1:
a: \(x\left(3-4x\right)+5\left(3-4x\right)=\left(3-4x\right)\left(x+5\right)\)
b: \(2y\left(5y-6\right)-4\left(6-5y\right)\)
\(=2y\left(5y-6\right)+4\left(5y-6\right)\)
\(=2\left(5y-6\right)\left(y+2\right)\)
c: \(=27\left(x-2\right)^3-3x\left(x-2\right)^2\)
\(=3\left(x-2\right)^2\cdot\left[9\left(x-2\right)-x\right]\)
\(=3\left(x-2\right)^2\left(8x-18\right)=6\left(x-2\right)^2\cdot\left(4x-9\right)\)
d: \(=6y\left(x-y\right)\left(x+y\right)-8y\left(x+y\right)^2\)
\(=2y\left(x+y\right)\left[3\left(x-y\right)-4\left(x+y\right)\right]\)
\(=2y\left(x+y\right)\left(3x-3y-4x-4y\right)\)
\(=2y\left(x+y\right)\left(-x-7y\right)\)
Bài 1
a) x(3 - 4x) + 5(3 - 4x)
= (3 - 4x)(x + 5)
b) 2y(5y - 6) - 4(6- 5y)
= 2y(5y - 6) + 4(5y - 6)
= (5y - 6)(2y + 4)
= 2(5y - 6)(y + 2)
c) 27(x - 2)³ - 3x(2 - x)²
= 27(x - 2)³ - 3x(x - 2)²
= 3(x - 2)²[9(x - 2) - x]
= 3(x - 2)²(9x - 18 - x)
= 3(x - 2)²(8x - 18)
= 6(x - 2)²(4x - 9)
d) 6y(x² - y²) - 8y(x + y)²
= 6y(x - y)(x + y) - 8y(x + y)²
= 2y(x + y)[3(x - y) - 4(x + y)]
= 2y(x + y)(3x - 3y - 4x - 4y)
= 2y(x + y)(-x - 7y)
= -2y(x + y)(x + 7y)
\(a,50\%x-0,2+x=\dfrac{4}{5}\)
\(\Leftrightarrow\dfrac{1}{2}x-0,2+x=\dfrac{4}{5}\)
\(\Leftrightarrow\dfrac{1}{2}x+x=\dfrac{4}{5}+0,2\)
\(\Leftrightarrow\dfrac{3}{2}x=\dfrac{4}{5}+\dfrac{1}{5}\)
\(\Leftrightarrow\dfrac{3}{2}x=1\)
\(\Leftrightarrow x=\dfrac{2}{3}\)
\(b,\left(x-\dfrac{3}{4}\right):\dfrac{1}{2}+\dfrac{3}{2}=\dfrac{25}{2}\)
\(\Leftrightarrow\left(x-\dfrac{3}{4}\right).2=\dfrac{25}{2}-\dfrac{3}{2}\)
\(\Leftrightarrow\left(x-\dfrac{3}{4}\right).2=\dfrac{22}{2}\)
\(\Leftrightarrow x-\dfrac{3}{4}=11:2\)
\(\Leftrightarrow x=\dfrac{11}{2}+\dfrac{3}{4}\)
\(\Leftrightarrow x=\dfrac{25}{4}\)
5^2 là năm mũ hai ak
\(=3\cdot25-27:9+25\cdot4-18:9=75-3+100-2=72+100-2=170\)