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1)
\((x+2)(x+3)(x+4)(x+5)-24\\=[(x+2)(x+5)]\cdot[(x+3)(x+4)]-24\\=(x^2+7x+10)(x^2+7x+12)-24\)
Đặt \(x^2+7x+10=y\), khi đó biểu thức trở thành:
\(y(y+2)-24\\=y^2+2y-24\\=y^2+2y+1-25\\=(y+1)^2-5^2\\=(y+1-5)(y+1+5)\\=(y-4)(y+6)\\=(x^2+7x+10-4)(x^2+7x+10+6)\\=(x^2+7x+6)(x^2+7x+16)\)
2) Bạn xem lại đề!
\(=16-\left(x^2-2xy+y^2\right)\)
\(=4^2-\left(x-y\right)^2=\left(4-x+y\right)\left(4+x-y\right)\)
\(x^2-4x+3=x^2-3x-x+3=x\left(x-3\right)-\left(x-3\right)=\left(x-1\right)\left(x-3\right)\)
\(x^2+5x+4=x^2+4x+x+4=x\left(x+4\right)+\left(x+4\right)=\left(x+1\right)\left(x+4\right)\)
\(x^2-x-6=x^2-3x+2x-6=x\left(x-3\right)+2\left(x-3\right)=\left(x+2\right)\left(x-3\right)\)
\(x^4+4=\left(x^2\right)^2+2.x^2.2+2^2-4x^2=\left(x^2+2\right)^2-4x^2=\left(x^2+2\right)^2-\left(2x^2\right)=\left(x^2+2+2x\right)\left(x^2-2-2x\right)\)
x11 + x10 + 1
= ( x11 - x9 + x8 - x6 + x5 - x3 + x2 ) + ( x10 - x8 + x7 - x5 + x4 - x2 + x ) + ( x9 - x7 + x6 - x4 + x3 - x + 1 )
= x2 ( x9 - x7 + x6 - x4 + x3 - x + 1 ) + x( ( x9 - x7 + x6 - x4 + x3 - x + 1 ) + 1( x9 - x7 + x6 - x4 + x3 - x + 1 )
= ( x2 + x + 1 ) ( x9 - x7 + x6 - x4 + x3 - x + 1 )
Chỗ nào không hiểu thì ib nhé :)
x11+x10+1
=x11+x10+x9-x9-x8-x7+x8+x7+x6-x6-x5-x4+x5+x4+x3-x3-x2-x+x2+x+1
=(x11+x10+x9)-(x9+x8+x7)+(x8+x7+x6)-(x6+x5+x4)+(x5+x4+x3)-(x3+x2+x)+(x2+x+1)
=x9(x2+x+1)-x7(x2+x+1)+x6(x2+x+1)-x4(x2+x+1)+x3(x2+x+1)-x(x2+x+1)+(x2+x+1)
=(x2+x+1)(x9-x7+x6-x4+x3-x+1)
= \(2\left(x^2+2x+1-y^2\right)=2\left[\left(x+1\right)^2-y^2\right]=2\left(x-y+1\right)\left(x+y+1\right)\)
\(x^2-y^2+6y-9=x^2-\left(y^2-6y+9\right)\)
\(=x^2-\left(y-3\right)^2\)
\(=\left(x+y-3\right)\left(x-y+3\right)\)
ko pt đc nha bạn
thanks