Question

Khai triển các biểu thức sau:

a. 25 - \(x^2\) e. \(x^6-1\)

b.-196 + \(4x^2\) g. \(-16+\left(x+3\right)^2\)

c. \(2^6-47^2\) h. \(64+\left(-49y^2\right)\)

d.\(5^4-81x^4\) i. \(\dfrac{25}{16}-9y^2\)

Answer 1

a. 25 - \(x^2\) = (5-x) (5+x)

b) -196 + 4\(x^2\) = 196 - 4\(x^2\) = (14- 2x) (14+2x)

c)\(5^4-81x^4\) = \(\left[\left(5^2\right)^2\right]-\left[\left(81x^2\right)^2\right]\) = (\(\left(5^2-81x^2\right)\left(5^2+81x^2\right)\)

Answer 2

\(a,25-e=\left(5-\sqrt{e}\right)\left(5+\sqrt{e}\right)\)

\(b,-196+g=-\left(196-g\right)=-\left(14-\sqrt{g}\right)\left(14+\sqrt{g}\right)\)

\(c,2^6-47^2=\left(2^3\right)^2-47^2=\left(2^3-47\right)\left(2^3+47\right)\)

\(d,5^4-81x^4=\left(5^2\right)^2-\left(9x^2\right)^2=\left(5^2-9x^2\right)\left(5^2+9x^2\right)=\left(25-9x^2\right)\left(25+9x^2\right)\)

\(i,\dfrac{25}{16}-9y^2=\left(\dfrac{5}{4}-3y\right)\left(\dfrac{5}{4}+3y\right)\)