81-(9-x^2)^2
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a: Ta có: \(\left(x^2+x-1\right)^2-\left(x^2+2x+3\right)^2\)
\(=\left(x^2+x-1-x^2-2x-3\right)\left(x^2+x-1+x^2+2x+3\right)\)
\(=\left(-x-4\right)\left(2x^2+3x+2\right)\)
b: Ta có: \(\left(x-3\right)^2-16\)
\(=\left(x-3-4\right)\left(x-3+4\right)\)
\(=\left(x+1\right)\left(x-7\right)\)
c: \(y^2+16y+64=\left(y+8\right)^2\)
b: \(3^4\cdot3^5:\dfrac{1}{27}==3^9\cdot3^3=3^{12}\)
(x - 3) ( x2 + 3x + 9 )
= ( x - 3 ).( x2 + x.3 + 32 )
= x3 - 33
= x3 - 27
a. (a2 - b2)2 - (a2 + b2)2
= (a2 - b2 - a2 - b2)(a2 - b2 + a2 + b2)
= -2b2 . 2a2
b. a6 - b6
<=> (a3)2 - (b3)2
<=> (a3 - b3)(a3 + b3)
\(a,\left(a^2-b^2\right)^2-\left(a^2+b^2\right)^2\\ =a^4-2a^2b^2+b^4-a^4-2a^2b^2-b^4\\ =-4a^2b^2\)
\(b,a^6-b^6=a^2\left(a^3-b^3\right)=a^2\left(a-b\right)\left(a^2+ab+b^2\right)\)
\(c,-4x^2+9y^2=\left(3y-2x\right)\left(3y+2x\right)\\ d,\left(x+1\right)^3-\left(2-x\right)^3\\ =\left(x+1-2+x\right)\left[\left(x+1\right)^2+\left(x+1\right)\left(2-x\right)+\left(2-x\right)^2\right]\\ =\left(2x-1\right)\left(x^2+2x+1-x^2+x+2+x^2-4x+4\right)\\ =\left(2x-1\right)\left(x^2-x+7\right)\)
\(e,8+\left(4x-3\right)^3\\ =\left(8+4x-3\right)\left[64-8\left(4x-3\right)+\left(4x-3\right)^2\right]\\ =\left(4x+5\right)\left(64-32x+24+16x^2-24x+9\right)\\ =\left(4x+5\right)\left(16x^2-56x+97\right)\)
\(g,81-\left(9-x^2\right)^2\\ =\left(9-9+x^2\right)\left(9+9-x^2\right)\\ =x^2\left(18-x^2\right)\left[=x^2\left(\sqrt{18}-x\right)\left(\sqrt{18}+x\right)\right]\)
Chỗ trong ngoặc nếu bạn chưa học căn thì ko cần ghi nha
a: \(\left(x+y+z\right)^2-\left(y+z\right)^2\)
\(=\left(x+y+z-y-z\right)\left(x+y+z+y+z\right)\)
\(=x\left(x+2y+2z\right)\)
b: \(\left(x-3\right)^2-2\left(x^2-9\right)+\left(x+3\right)^2\)
\(=\left(x-3-x-3\right)^2\)
=36
c: \(\left(a^2-b^2\right)^2-\left(a+b^2\right)^2\)
\(=\left(a^2-b^2-a-b^2\right)\left(a^2-b^2+a+b^2\right)\)
\(=\left(a^2-a-2b^2\right)\left(a^2+a\right)\)
\(=a\cdot\left(a+1\right)\left(a^2-a-2b^2\right)\)
Ta có: \(81+\left(9-x^2\right)^2\)
Tương tự: \(81+-x^4+18x^2+-81\)
\(=\left(-x^4\right)+\left(18x^2\right)+\left(81+-81\right)\)
\(=-x^4+18x^2\)
\(81-\left(9-x^2\right)^2\)
\(=\)\(9^2-\left(3^2-x^2\right)^2\)
\(=\)\(9^2-\left(9-x^2\right)^2\)
\(=\)\(\left(9-9+x\right)\left(9+9-x\right)\)
\(=\)\(x\left(18-x\right)\)
Chúc bạn học tốt ~