\(a.\frac{\frac{x-3}{5}+1}{4}=\frac{\frac{2x}{3}-\frac{1}{2}}{6}\\ b.\frac{5x+\frac{x+2}{2}}{9}=\frac{\frac{x+3}{5}+15}{12}-2\)
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\(\Leftrightarrow\frac{3x-3+5}{20}=|\frac{4x-3}{36}|\)
\(\Leftrightarrow\frac{3x+2}{5}=|\frac{4x-3}{9}|\)
\(\Leftrightarrow\left(3x+2\right)9=5|4x-3|\)
ĐK: \(3x+2\ge0\Rightarrow x\ge\frac{-2}{3}\)
\(\Leftrightarrow\orbr{\begin{cases}5.\left(4x-3\right)=9.\left(3x+2\right)\\-5.\left(4x-3\right)=9.\left(3x+2\right)\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}20x-15=27x+18\\-20x+15=27x+18\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}7x=-33\\-47x=3\end{cases}\Leftrightarrow\orbr{\begin{cases}x=\frac{-33}{7}\left(L\right)\\x=\frac{-3}{47}\end{cases}}}\)
Vậy x= - 3/47
b) \(\Leftrightarrow\frac{10x+x+2}{18}=\frac{x+3+75}{60}-2\)
\(\Leftrightarrow\frac{11x+2}{18}=\frac{x-42}{60}\)
\(\Leftrightarrow10.\left(11x+2\right)=3.\left(x-42\right)\)
\(\Leftrightarrow110x+20=3x-126\)
\(\Leftrightarrow107x=-146\Leftrightarrow x=\frac{-146}{107}\)
Ta có : \(a+b=2\)
\(\Rightarrow\)\(a = 2 -b\)
\(A = 2a^2 +3b^2 +3ab\)
\(A = 2a^2 + 3b. (a+b)\)
\(A = 2. (2-b)^2+3b. (2-b+b)\)
\(A = 2. ( b^2 -4b+4)+6b\)
\(A = 2b^2 -8b+8+6b\)
\(A = 2b^2 -2b+8\)
\(A = 2. ( b ^2 -b+4)\)
\(A=2. (b^2 -2.b.{1\over2}+({1\over2})^2-({1\over2})^2+4)\)
\(A = 2. [ (b -{1\over2})^2-{15\over4}]\)
\(A =2. (b-{1\over2})^2 + {15\over2}\)\(\ge\)\({15\over2}\)
\(Min A ={15\over2}\)\(\Leftrightarrow\)\(a = {3\over2};b={1\over2}\)
Ta có : a+b=2→b=2−a
→P=2a2+3b2+3ab=2a2+3b(a+b)=2a2+3b.2=2a2+6b=2a2+6(2−a)=2a2−6a+12
→P=2(a2−3a)+12
→P=2(a2−2a.32+94)+152
→P=2(a−32)2+152≥152
→GTNNP=152
Dấu = xảy ra khi a−32=0
a) \(ĐKXĐ:\hept{\begin{cases}x\ne0\\x\ne\pm5\end{cases}}\)
\(M=\left(\frac{x}{x+5}-\frac{5}{5-x}+\frac{10x}{x^2-25}\right)\cdot\left(1-\frac{5}{x}\right)\)
\(\Leftrightarrow M=\frac{x^2-5x+5x+25+10x}{\left(x+5\right)\left(x-5\right)}\cdot\frac{x-5}{x}\)
\(\Leftrightarrow M=\frac{\left(x^2+10x+25\right)\left(x-5\right)}{\left(x+5\right)\left(x-5\right)x}\)
\(\Leftrightarrow M=\frac{\left(x+5\right)^2}{x\left(x+5\right)}\)
\(\Leftrightarrow M=\frac{x+5}{x}\)
b) Để \(M\inℤ\)
\(\Leftrightarrow x+5⋮x\)
\(\Leftrightarrow5⋮x\)
\(\Leftrightarrow x\inƯ\left(5\right)=\left\{\pm1;\pm5\right\}\)
Mà \(x\ne\pm5\)
\(\Leftrightarrow x\in\left\{1;-1\right\}\)
Vậy để \(M\inℤ\Leftrightarrow x\in\left\{1;-1\right\}\)
\(M=\left(\frac{x}{x+5}-\frac{5}{5-x}+\frac{10x}{x^2-25}\right)\cdot\left(1-\frac{5}{x}\right)\left(x\ne\pm5;x\ne0\right)\)
\(\Leftrightarrow M=\left(\frac{x}{x+5}+\frac{5}{x-5}+\frac{10x}{\left(x-5\right)\left(x+5\right)}\right)\cdot\frac{x-5}{x}\)
\(\Leftrightarrow M=\left(\frac{x^2-5x}{\left(x-5\right)\left(x+5\right)}+\frac{5x+25}{\left(x-5\right)\left(x+5\right)}+\frac{10x}{\left(x-5\right)\left(x+5\right)}\right)\cdot\frac{x-5}{x}\)
\(\Leftrightarrow M=\frac{x^2-5x+5x+25+10x}{\left(x-5\right)\left(x+5\right)}\cdot\frac{x-5}{x}\)
\(\Leftrightarrow M=\frac{x^2+10x+25}{\left(x-5\right)\left(x+5\right)}\cdot\frac{x-5}{x}\)
\(\Leftrightarrow M=\frac{\left(x+5\right)^2\left(x-5\right)}{\left(x-5\right)\left(x+5\right)x}=\frac{x+5}{x}\)
b) M là số nguyên thì x+5 chia hết cho x
=> 5 chia hết cho x
x nguyên => x thuộc Ư (5)={-5;-1;1;5}
Vậy x={-5;-1;1;5} thì M là số nguyên
x⁴ - 4x² + 12x - 9 = 0
<=> x⁴ - x³ + x³ - x² - 3x² + 3x + 9x - 9 = 0
<=> x³(x - 1) + x²(x - 1) - 3x(x - 1) + 9(x - 1) = 0
<=> (x - 1)(x³ + x² - 3x + 9) = 0
<=> (x - 1)(x³ + 3x² - 2x² - 6x + 3x + 9) = 0
<=> (x - 1)[ x²(x + 3) - 2x(x + 3) + 3(x + 3) ] = 0
<=> (x - 1)(x + 3)(x² - 2x + 3) = 0
<=> (x - 1)(x + 3)(x² - 2x + 1 + 2) = 0
<=> (x - 1)(x + 3)[ (x - 1)² + 2 ] = 0
<=> (x - 1)(x + 3) = 0 --> do (x - 1)² + 2 > 0 với mọi x
<=>
[ x - 1 = 0 =>[ x = 1
[ x + 3 = 0 =>[ x = -3
Bạn nên sửa >= là = vì giải bất phương trình mà
a)\(\frac{\frac{x-3}{5}+1}{4}=\frac{\frac{2x}{3}-\frac{1}{2}}{6}\)
\(\Rightarrow\frac{\frac{x-3+5}{5}}{4}=\frac{\frac{4x}{6}-\frac{3}{6}}{6}\)
\(\Rightarrow\frac{\frac{x+2}{5}}{4}=\frac{\frac{4x-3}{6}}{6}\)
\(\Rightarrow\frac{x+2}{5}:4=\frac{4x-3}{6}:6\)
\(\Rightarrow\frac{x+2}{5}.\frac{1}{4}=\frac{4x-3}{6}.\frac{1}{6}\)
\(\Rightarrow\frac{x+2}{20}=\frac{4x-3}{36}\)
\(\Rightarrow36.\left(x+2\right)=20.\left(4x-3\right)\)
\(\Rightarrow36x+72=80x-60\)
\(\Rightarrow72+60=80x-36x\)
\(\Rightarrow132=44x\)
\(\Rightarrow x=\frac{132}{44}=3\)
Vậy x=3
b)Bn làm tương tự phần a nha
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