9(x+5)2 - (x-7)2
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NH
1
25 tháng 11 2017
Ta có:\(9\left(x+5\right)^2-4\left(x-7\right)^2=9\left(x^2+10x+25\right)-4\left(x^2-14x+49\right)\)
\(=9x^2+90x+225-4x^2+56x-196=5x^2+146x+29\)
\(=\left(5x^2+145x\right)+\left(x+29\right)=\left(x+29\right)\left(5x+1\right)\)
SX
1
DP
1
26 tháng 6 2018
\(9\left(x-5\right)^2-\left(x+7\right)^2\)
\(=\)\(3^2\left(x-5\right)^2-\left(x+7\right)^2\)
\(=\)\(\left[3\left(x-5\right)\right]^2-\left(x+7\right)^2\)
\(=\)\(\left(3x-15\right)^2-\left(x+7\right)^2\)
\(=\)\(\left(3x-15-x-7\right)\left(3x-15+x+7\right)\)
\(=\)\(\left(2x-22\right)\left(4x-8\right)\)
\(=\)\(2\left(x-11\right).4\left(x-2\right)\)
\(=\)\(8\left(x-11\right)\left(x-2\right)\)
Chúc bạn học tốt ~
NT
2
1 tháng 11 2021
\(=5^{^2}.\left(x+5\right)^2-3^2.\left(x+7\right)^2\)
\(=\left(5x+25\right)^2-\left(3x+21\right)^2\)
\(=\left(5x+25+3x+21\right)\left(5x+25-3x-21\right)\)
\(=\left(8x+46\right)\left(2x+4\right)\)
\(=4\left(2x+23\right)\left(x+2\right)\)
1 tháng 11 2021
= 52 ( x + 5)2 - 32 (x +7)2
=[ 5 ( x +5) ]2 - [ 3 ( x + 7) ]2
= ( 5x + 25)2 - ( 3x + 21)2
= ( 5x + 25 - 3x - 21) - ( 5x + 25 + 3x + 21)
= ( 2x +4) - ( 8x +46)
= -6x - 42
= -6 ( x + 7)
C
1
1 tháng 11 2020
M = x9 - x7 + x6 - x5 - x4 + x3 - x2 + 1
= ( x9 - x7 ) + ( x6 - x4 ) - ( x5 - x3 ) - ( x2 - 1 )
= x7( x2 - 1 ) + x4( x2 - 1 ) - x3( x2 - 1 ) - ( x2 - 1 )
= ( x2 - 1 )( x7 + x4 - x3 - 1 )
= ( x - 1 )( x + 1 )[ x4( x3 + 1 ) - ( x3 + 1 ) ]
= ( x - 1 )( x + 1 )( x3 + 1 )( x4 - 1 )
= ( x - 1 )( x + 1 )( x + 1 )( x2 - x + 1 )( x2 - 1 )( x2 + 1 )
= ( x + 1 )2( x - 1 )( x2 - x + 1 )( x - 1 )( x + 1 )( x2 + 1 )
= ( x + 1 )3( x - 1 )2( x2 + 1 )( x2 - x + 1 )
MD
0
NH
4
DN
6 tháng 11 2016
Ta có:
\(x^9-x^7-x^6-x^5+x^4+x^3+x^2-1\)
\(=\left(x^9-x^8\right)+\left(x^8-x^7\right)-\left(x^6-x^5\right)-\left(2x^5-2x^4\right)-\left(x^4-x^3\right)+\left(x^2-x\right)+\left(x-1\right) \)
\(=x^8.\left(x-1\right)+x^7.\left(x-1\right)-x^5.\left(x-1\right)-2x^4.\left(x-1\right)-x^3\left(x-1\right)+x\left(x-1\right)+\left(x-1\right)\)
\(=\left(x-1\right)\left(x^8+x^7-x^5-2x^4-x^3+x+1\right)\)
C
1
1 tháng 9 2021
h: Ta có: \(x\left(x+2\right)\left(x+4\right)\left(x+6\right)+15\)
\(=\left(x^2+6x\right)\left(x^2+6x+8\right)+15\)
\(=\left(x^2+6x\right)^2+8\left(x^2+6x\right)+15\)
\(=\left(x^2+6x+3\right)\left(x^2+6x+5\right)\)
\(=\left(x+1\right)\left(x+5\right)\left(x^2+6x+3\right)\)
9(x + 5)^2 - (x + 7)^2
<=>[3(x+5)]^2 - (x+7)^2
<=>[(3(x+5)-(x+7)] [(3(x+5)+(x+7)]
<=>(3x+15-x-7)(3x+15+x+7)
<=>(2x+8)(4x+22)
<=>2(x+4) . 2(2x+11)
<=>4(x+4)(2x+11)
9(x + 5)^2 - (x + 7)^2
<=>[3(x+5)]^2 - (x+7)^2
<=>[(3(x+5)-(x+7)] [(3(x+5)+(x+7)]
<=>(3x+15-x-7)(3x+15+x+7)
<=>(2x+8)(4x+22)
<=>2(x+4) . 2(2x+11)
<=>4(x+4)(2x+11)