5x - 2 = 1
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A = (5\(x\) + 1)2 + (5\(x\) - 1)2 - 2.( 5\(x\) +1).(5\(x\) - 1) tại \(x\) = 1
Thay \(x\) = 1 vào A ta có:
A = (5.1 + 1)2 + (5.1 - 1)2 - 2.(5.1 + 1).(5.1 - 1)
A = 62 + 42 - 2.6.4
A = 36 + 16 - 48
A = 52 - 48
A = 4
\(\left(5x-1\right)^2+2\left(1-5x\right)\left(4+5x\right)+\left(5x+4\right)^2\)
\(=\left(5x-1\right)^2-2\left(5x-1\right)\left(5x+4\right)+\left(5x+4\right)^2\)
\(=\left[\left(5x-1\right)-\left(5x+4\right)\right]^2\)
\(=\left(5x-1-5x-4\right)^2\)
\(=\left(-5\right)^2\)
\(=25\)
(x2-5x+1)2+2(5x-1)(x2-5x+1)+(5x-1)2
= [(x2-5x+1)+(5x-1)]2
= (x2-5x+1+5x-1)2
= (x2)2
= x4
(x2 - 5x + 1)2 + 2(5x - 1)(x2 - 5x + 1) + (5x - 1)2 = (x2 - 5x + 1 + 5x - 1)2 = (x2)2 = x4
\(5^x+5^{x+1}+5^{x+2}+5^{x+3}=1+2+3+...+87+88-4^2\)
=>\(5^x+5^x\cdot5+5^x\cdot25+5^x\cdot125=88\cdot\dfrac{\left(88+1\right)}{2}-16\)
=>\(156\cdot5^x=44\cdot89-16=3900\)
=>\(5^x=\dfrac{3900}{156}=25\)
=>x=2
C = ( x2 - 5x + 1 )2 + ( 5x - 1 )2 + 2( x2 - 5x + 1 )( 5x - 1 )
= [ ( x2 - 5x + 1 ) + ( 5x - 1 ) ]2 ( HĐT số 1 )
= ( x2 - 5x + 1 + 5x - 1 )2
= ( x2 )2 = x4
(5x-1)^2+2(5x-1)(5x+1)+5(2x-1)
=25x^2-10x+1+2(25x^2-1)+10x-5
=25x^2-4+50x^2-2
=75x^2-6
\(\left(5x-1\right)^2+2\left(5x-1\right)\left(5x+1\right)+5\left(2x-1\right)\)
\(=25x^2-10x+1+2\left(25x^2-1\right)+10x-5\)
\(=25x^2-10x+1+50x^2-2+10x-5\)
\(=\left(25x^2+50x^2\right)+\left(10x-10x\right)+\left(1-2-5\right)\)
\(=75x^2-6\)
P = (5x − 1) + 2(1 − 5x)(4 + 5x) + (5x+4)\(^2\)
= 5x – 1 + (2 – 10x).( 4+ 5x) + (5x+4)\(^2\)
= 5x – 1 + 8 + 10x – 40x – 50x\(^2\) + 25x\(^2\) + 40x + 16
= ( - 50x\(^2\) + 25x\(^2\) ) + ( 5x + 10x – 40x + 40x) + ( - 1+ 8 + 16 )
= -25x\(^2\) + 15x + 23
\(5x-2=1\)
\(5x\) \(=1+2\)
\(5x\) \(=3\)
\(x=3:5\)
\(x=0,6\)
x ko có giá trị