CHO 2 BIET THUC A= x- can x binh/x-1 va
B= x-4/x+2 can x binh
a. rut gon a va b
Những câu hỏi liên quan
cho 2 bieu thuc A=x+x^2/2-x va B=2x/x+1+3/x-2-2x^2+1/x^2-x-2 a, tinh gia tri cua A khi /2x-3/=1 b,tim dieu kien xac dinh va rut gon bieu thuc B c,tim so nguyen x de P=A.B dat gia tri lon nhat
mk dang can gap
a:
ĐKXĐ: x<>2
|2x-3|=1
=>\(\left[{}\begin{matrix}2x-3=1\\2x-3=-1\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}x=2\left(loại\right)\\x=1\left(nhận\right)\end{matrix}\right.\)
Thay x=1 vào A, ta được:
\(A=\dfrac{1+1^2}{2-1}=\dfrac{2}{1}=2\)
b: ĐKXĐ: \(x\notin\left\{-1;2\right\}\)
\(B=\dfrac{2x}{x+1}+\dfrac{3}{x-2}-\dfrac{2x^2+1}{x^2-x-2}\)
\(=\dfrac{2x}{x+1}+\dfrac{3}{x-2}-\dfrac{2x^2+1}{\left(x-2\right)\left(x+1\right)}\)
\(=\dfrac{2x\left(x-2\right)+3\left(x+1\right)-2x^2-1}{\left(x+1\right)\left(x-2\right)}\)
\(=\dfrac{2x^2-4x+3x+3-2x^2-1}{\left(x+1\right)\left(x-2\right)}\)
\(=\dfrac{-x+2}{\left(x+1\right)\left(x-2\right)}=-\dfrac{1}{x+1}\)
c: \(P=A\cdot B=\dfrac{-1}{x+1}\cdot\dfrac{x\left(x+1\right)}{2-x}=\dfrac{x}{x-2}\)
\(=\dfrac{x-2+2}{x-2}=1+\dfrac{2}{x-2}\)
Để P lớn nhất thì \(\dfrac{2}{x-2}\) max
=>x-2=1
=>x=3(nhận)
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Rut gon cac bieu thuc sau:
a, (x+3)(x-4)-(x-1)(x+2)
b, a3+b3+3.a2.b+3ab2
Ai lam nhanh nhat va day du nhat thi to se tick cho
(Nho lam day du moi tick nhe,ko can lam het ca 2 cau ,biet lam cau nao thi lam cau do)
a,(x+2)(x-2)-(x-3)(x+1)
= x^2 - 2^2 - ( x^2 + x - 3x - 3 )
= x^2 - 4 - x^2 - x + 3x +3
= 2x -1
duyệt đi olm
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còn lâu mới nhanh đc, đi ,rồi giải cho
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Cho cac so nguyen duong a,b,c,x,y,z1, Biet 1/a 3/b + c 5/c + a. Hay rut gon phan so A a/2b - c2. Biet a/b 2b/cc 4c/a. Hay rut gon phan so B ab + bc + ca/a2 + b + c23. Biet x/a y/b z/c. Hay rut gon phan so C x*y*z*(b+c)*(c+a)*(a+b)/a*b*c(y+z)*(z+x)*(x+y)4. Biet ab/a + 2b 2/5; bc/b + 2c 3/4; ca/c +2a 3/5. Hay rut gon phan so D abc/ab+bc+ca5. Biet 3/a -4b 5c. Hay rut gon phan so E 3bc + ab - 4ac/6bc - 8ac -abGiup minh nhe! Ai lam duoc va dung cho tick.Thanks cac ban
Đọc tiếp
Cho cac so nguyen duong a,b,c,x,y,z
1, Biet 1/a = 3/b + c = 5/c + a. Hay rut gon phan so A = a/2b - c
2. Biet a/b = 2b/cc = 4c/a. Hay rut gon phan so B = ab + bc + ca/a2 + b + c2
3. Biet x/a = y/b =z/c. Hay rut gon phan so C = x*y*z*(b+c)*(c+a)*(a+b)/a*b*c(y+z)*(z+x)*(x+y)
4. Biet ab/a + 2b = 2/5; bc/b + 2c = 3/4; ca/c +2a = 3/5. Hay rut gon phan so D = abc/ab+bc+ca
5. Biet 3/a -4b = 5c. Hay rut gon phan so E = 3bc + ab - 4ac/6bc - 8ac -ab
Giup minh nhe! Ai lam duoc va dung cho tick.
Thanks cac ban
xin lỗi tớ ấn nhầm chỗ M=7 tớ làm lại rồi đó
ban tra loi het cac cau hoi phia tren kia ho minh dc ko?
Cho cac so nguyen duong a,b,c,x,y,z1, Biet 1/a 3/b + c 5/c + a. Hay rut gon phan so A a/2b - c2. Biet a/b 2b/cc 4c/a. Hay rut gon phan so B ab + bc + ca/a2 + b + c23. Biet x/a y/b z/c. Hay rut gon phan so C x*y*z*(b+c)*(c+a)*(a+b)/a*b*c(y+z)*(z+x)*(x+y)4. Biet ab/a + 2b 2/5; bc/b + 2c 3/4; ca/c +2a 3/5. Hay rut gon phan so D abc/ab+bc+ca5. Biet 3/a -4b 5c. Hay rut gon phan so E 3bc + ab - 4ac/6bc - 8ac -abGiup minh nhe! Ai lam duoc va dung cho tick.Thanks cac ban
Đọc tiếp
Cho cac so nguyen duong a,b,c,x,y,z
1, Biet 1/a = 3/b + c = 5/c + a. Hay rut gon phan so A = a/2b - c
2. Biet a/b = 2b/cc = 4c/a. Hay rut gon phan so B = ab + bc + ca/a2 + b + c2
3. Biet x/a = y/b =z/c. Hay rut gon phan so C = x*y*z*(b+c)*(c+a)*(a+b)/a*b*c(y+z)*(z+x)*(x+y)
4. Biet ab/a + 2b = 2/5; bc/b + 2c = 3/4; ca/c +2a = 3/5. Hay rut gon phan so D = abc/ab+bc+ca
5. Biet 3/a -4b = 5c. Hay rut gon phan so E = 3bc + ab - 4ac/6bc - 8ac -ab
Giup minh nhe! Ai lam duoc va dung cho tick.
Thanks cac ban
Bai 1)Cho bieu thuc Afrac{x+y-2sqrt{xy}}{x-y}a)Tim dieu kien de A co nghiab)Rut gon Ac)Tinh A biet x3+2sqrt{2}va y3-2sqrt{2}Bai 2) Cho bieu thuc Bfrac{x-3}{sqrt{x-1}-sqrt{2}}a)Tim dieu kien de B co nghiab)Rut gon Bc) Tinh B voi x4left(2-sqrt{3}right)d)Tim x de B co gia tri nho nhat
Đọc tiếp
Bai 1)Cho bieu thuc A=\(\frac{x+y-2\sqrt{xy}}{x-y}\)
a)Tim dieu kien de A co nghia
b)Rut gon A
c)Tinh A biet x=\(3+2\sqrt{2}\)va y=\(3-2\sqrt{2}\)
Bai 2) Cho bieu thuc B=\(\frac{x-3}{\sqrt{x-1}-\sqrt{2}}\)
a)Tim dieu kien de B co nghia
b)Rut gon B
c) Tinh B voi x=\(4\left(2-\sqrt{3}\right)\)
d)Tim x de B co gia tri nho nhat
a) A có nghĩa\(\Leftrightarrow x-y\ne0\Leftrightarrow x\ne y\)
b) \(A=\frac{x+y-2\sqrt{xy}}{x-y}=\frac{\left(\sqrt{x-\sqrt{y}}\right)^2}{\left(\sqrt{x}+\sqrt{y}\right)\left(\sqrt{x}-\sqrt{y}\right)}=\frac{\sqrt{x}-\sqrt{y}}{\sqrt{x}+\sqrt{y}}\)
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cho 2 bieu thuc:
A=(\(\sqrt{20}\) -\(\sqrt{45}\) +3\(\sqrt{5}\) ).\(\sqrt{5}\) va B=\(\dfrac{x+1-2\sqrt{x}}{\sqrt{x}-1}\) +\(\dfrac{x+\sqrt{x}}{\sqrt{x}+1}\) (Dieu kien: x>0, x khac 1
a) Rut gon bieu thuc A va B
b)Tim cac gia tri cua x de gia tri cua bieu thuc A bang 2lan gia tri B
a: \(A=\left(2\sqrt{5}-3\sqrt{5}+3\sqrt{5}\right)\cdot\sqrt{5}=2\sqrt{5}\cdot\sqrt{5}=10\)
\(B=\dfrac{\left(\sqrt{x}-1\right)^2}{\sqrt{x}-1}+\dfrac{\sqrt{x}\left(\sqrt{x}+1\right)}{\sqrt{x}+1}\)
\(=\sqrt{x}-1+\sqrt{x}=2\sqrt{x}-1\)
b: A=2B
=>\(10=4\sqrt{x}-2\)
=>\(4\sqrt{x}=12\)
=>x=9(nhận)
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Rut gon va tinh gia tri bieu thuc
A= (x-4).(x-2)-(x-1).(x-3) tại x= \(1\dfrac{3}{4}\)
Ta có:
\(A=\left(x-4\right)\left(x-2\right)-\left(x-1\right)\left(x-3\right)\)
\(A=\left(x^2-4x-2x+8\right)-\left(x^2-x-3x+4\right)\)
\(A=\left(x^2-6x+8\right)-\left(x^2-4x+4\right)\)
\(A=x^2-6x+8-x^2+4x-4\)
\(A=-2x+4\)
Thay \(x=1\dfrac{3}{4}=\dfrac{7}{4}\) vào A ta được:
\(A=-2.\dfrac{7}{4}+4\)
\(A=-\dfrac{7}{2}+4\)
\(A=\dfrac{1}{2}\)
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Cho x/a =y/b =z/c va a b c x y z khac 0 rut gon bieu thuc b = ( a^2x + b^2y + c^2z ) / x^3 +y^3+z^3
Thuc hien phep nhan rut gon roi tinh gia tri bieu thuc
B)x(x^2-y)-x^2(x+y)+y(x^2-x) tai x=1/2 va y=-100
=x^3-xy-x^3-x^2y+x^2y--xy
=-2xy
thay x=1\2 va y bang 100 vao Bta duoc
B= -2.1\2.100=-100
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