bài 5; tìm x
f, a mũ 2 + x - x mũ 2 - a = 0
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D = x\(^2\) + 2xy + y\(^2\) - z\(^2\) - 2zt - t\(^2\)
D = (x + y)\(^2\) - z\(^2\) + z\(^2\) - 2zt + t\(^2\) - t\(^2\)
D = (89 + 11)\(^2\) +(z - t)\(^2\) - z\(^2\) - t\(^2\)
D = 100\(^2\) + (60 - 30)\(^2\) - 60\(^2\) - 30\(^2\)
D = 10 000 + 900 - 3600 - 900
D = 6400
Học tốt
Ta có : A = 2 x ( X + 1 ) + X + 1
= ( X + 1 ) x ( 2 + 1 )
= ( X + 1 ) x 3
Thay X = 99 vào biểu thức ta có :
( 99 + 1 ) x 3 = 300
e, A = 2x ( x + 1 ) + x + 1 tại x =99
A = 2 x 99 x ( 99 + 1 ) + 99 + 1
A = 198 x 100 + 100
A = 19800 + 100
A = 19900
Bài 5 :
f, bạn xem lại đề hay là tìm x chứa tham số a ?
g, \(x^2+3x-\left(2x+6\right)=0\Leftrightarrow x\left(x+3\right)-2\left(x+3\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left(x+3\right)=0\Leftrightarrow x=-3;x=2\)
h, \(5x+20-x^2-4x=0\Leftrightarrow5\left(x+4\right)-x\left(x+4\right)=0\)
\(\Leftrightarrow\left(5-x\right)\left(x+4\right)=0\Leftrightarrow x=-4;x=5\)
m, \(x^3-5x^2-x+5=0\Leftrightarrow x^2\left(x-5\right)-\left(x-5\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(x+1\right)\left(x-5\right)=0\Leftrightarrow x=\pm1;x=5\)
n, \(x\left(x-3\right)-7x+21=0\Leftrightarrow x\left(x-3\right)-7\left(x-3\right)=0\)
\(\Leftrightarrow\left(x-7\right)\left(x-3\right)=0\Leftrightarrow x=3;x=7\)
Bài 5 :
a, \(2x\left(x-3\right)+x-3=0\Leftrightarrow\left(2x+1\right)\left(x-3\right)=0\Leftrightarrow x=-\frac{1}{2};x=3\)
b, \(x\left(x+1\right)-x-1=0\Leftrightarrow\left(x-1\right)\left(x+1\right)=0\Leftrightarrow x=\pm1\)
c, sửa đề \(x^3-3x^2+x-3=0\Leftrightarrow x^2\left(x-3\right)+x-3=0\)
\(\Leftrightarrow\left(x^2+1>0\right)\left(x-3\right)=0\Leftrightarrow x=3\)
d, \(3x^2\left(2x-1\right)+1-4x^2=0\Leftrightarrow3x^2\left(2x-1\right)+\left(1-2x\right)\left(1+2x\right)=0\)
\(\Leftrightarrow\left(2x-1\right)\left(3x^2-2x-1\right)=0\Leftrightarrow\left(2x-1\right)\left(3x+1\right)\left(x-1\right)=0\Leftrightarrow x=1;x=-\frac{1}{3};x=\frac{1}{2}\)
e, \(x^3+2x-x^2-2=0\Leftrightarrow x\left(x^2+2\right)-\left(x^2+2\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(x^2+2>0\right)=0\Leftrightarrow x=1\)
a, \(\left(x+3\right)^2-\left(x+2\right)\left(x-2\right)=11\)
\(\Leftrightarrow x^2+6x+9-x^2+4=11\Leftrightarrow6x+2=0\Leftrightarrow x=-\frac{1}{3}\)
b, \(x^2-6x-7=0\Leftrightarrow\left(x+1\right)\left(x-7\right)=0\Leftrightarrow x=-1;x=7\)
c, \(\left(2x+1\right)^2-\left(3x-2\right)^2=0\Leftrightarrow\left(-x+3\right)\left(5x-1\right)=0\Leftrightarrow x=\frac{1}{5};x=3\)
Bài 3 :
\(D=40^2-28^2+32^2+80.32=40^2+2.40.32+32^2-28^2\)
\(=\left(40+32\right)^2-28^2=72^2-28^2=\left(72+28\right)\left(72-28\right)=46.100=4600\)
Bài 4 :
\(B=\left(9+1\right)\left(9^2+1\right)...\left(9^{32}+1\right)\)
\(8B=\left(9^2-1\right)\left(9^2+1\right)...\left(9^{32}+1\right)=9^{64}-1\)
\(\Rightarrow B=\frac{9^{64}-1}{8}< 9^{64}-1\Rightarrow B< C\)
B= 7800 nha
x=3
a=2