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\(=y\left(4x^2-4xy+y^2-49\right)\)
\(=y\left[\left(2x-y\right)^2-49\right]\)
\(=y\left(2x-y-7\right)\left(2x-y+7\right)\)
a) Ta có: \(4x^2-28xy+49y^2\)
\(=\left(2x\right)^2-2\cdot2x\cdot7y+\left(7y\right)^2\)
\(=\left(2x-7y\right)^2\)
b) Ta có: \(x^2+8xy+16y^2\)
\(=x^2+2\cdot x\cdot4y+\left(4y\right)^2\)
\(=\left(x+4y\right)^2\)
c) Ta có: \(x^2-12x+36\)
\(=x^2-2\cdot x\cdot6+6^2\)
\(=\left(x-6\right)^2\)
Bài 1:
b: \(=\left(x^2+x+4\right)^2+3x\left(x^2+x+4\right)+5x\left(x^2+x+4\right)+15x^2\)
\(=\left(x^2+x+4+3x\right)\left(x^2+x+4+5x\right)\)
\(=\left(x^2+4x+4\right)\left(x^2+6x+4\right)\)
\(=\left(x+2\right)^2\cdot\left(x^2+6x+4\right)\)
c: \(=25x^2-49y^2-\left(5x+7y\right)\)
\(=\left(5x-7y\right)\left(5x+7y\right)-\left(5x+7y\right)\)
\(=\left(5x+7y\right)\left(5x-7y-1\right)\)
d: \(8x^3-36x^2+54x-27=\left(2x-3\right)^3\)
1.a) (4x - 6y)2 - (8xy - 5)2 = (4x - 6y - 8xy + 5)(4x - 6y + 8xy - 5)
b) 16x2 - 49y2 = (4x)2 - (7y)2 = (4x - 7y)(4x + 7y)
c) 36x2 + 60x + 25 = (6x)2 + 2.6x.5 + 52 = (6x + 5)2
d) (2x - y)(x - y) - (3y - 4x)2 + (y - 2x)(2y - 3x) = (y - 2x)(y - x) + (y - 2x)(2y - 3x) - (3y - 4x)2
= (y - 2x)[(y - x) + (2y - 3x)] - (3y - 4x)2 = (y - 2x)(3y - 4x) - (3y - 4x)2 = (3y - 4x)[(y - 2x) - (3y - 4x)] = 2(3y - 4x)(x - y)
2.M = (3x - 4)(9x2 - 12x + 16) + (6x - 8)2 = (3x - 4)[(3x)2 - 2.3x.4 + 42] + [2(3x - 4)]2 = (3x - 4)(3x - 4)2 + 4(3x - 4)2
= (3x - 4)2(3x - 4 + 4) = 3x(3x - 4)2
a. 25 - \(x^2\) = (5-x) (5+x)
b) -196 + 4\(x^2\) = 196 - 4\(x^2\) = (14- 2x) (14+2x)
c)\(5^4-81x^4\) = \(\left[\left(5^2\right)^2\right]-\left[\left(81x^2\right)^2\right]\) = (\(\left(5^2-81x^2\right)\left(5^2+81x^2\right)\)
\(a,25-e=\left(5-\sqrt{e}\right)\left(5+\sqrt{e}\right)\)
\(b,-196+g=-\left(196-g\right)=-\left(14-\sqrt{g}\right)\left(14+\sqrt{g}\right)\)
\(c,2^6-47^2=\left(2^3\right)^2-47^2=\left(2^3-47\right)\left(2^3+47\right)\)
\(d,5^4-81x^4=\left(5^2\right)^2-\left(9x^2\right)^2=\left(5^2-9x^2\right)\left(5^2+9x^2\right)=\left(25-9x^2\right)\left(25+9x^2\right)\)
\(i,\dfrac{25}{16}-9y^2=\left(\dfrac{5}{4}-3y\right)\left(\dfrac{5}{4}+3y\right)\)
\(4x^2-49y^2+4x+1\)
\(=\left(4x^2+4x+1\right)-49y^2\)
\(=\left(2x+1\right)^2-\left(7y\right)^2\)
\(=\left(2x-7y+1\right)\left(2x+7y+1\right)\)