Đáp án:
Giải thích các bước giải:
bài 4:
a,8x-8y
=8(x-y)
b,4-$y^{2}$
=(2-y)(2+y)
c,7x(8-y)+5y(y-8)
=(8-y)(7x+5y)
d,$x^{3}$-6$x^{2}$+8x
=x($x^{2}$-6x+8)
=x(x+2)(x+4)
e,$x^4$+64
=($x^{2}$+4x+8)($x^{2}$-4x+8)
g,$x^{5}+$x^{4}$+1
=($x^{2}$+x+1)($x^{3}$-x+1)
bài 2:
a,4$x^{2}$-5x=0
⇔x(4x-5)=0
⇔\(\left[ \begin{array}{l}x=0\\x=5/4\end{array} \right.\)
b,5x(x+3)-4x-12=0
⇔5x(x+3)-4(x+3)=0
⇔(x+3)(5x-4)=0
⇔\(\left[ \begin{array}{l}x=-3\\x=4/5\end{array} \right.\)
c,$x^{2}$-1=x+1
⇔(x-1)(x+1)=x+1
⇔(x-1)(x+1)-(x+1)=0
⇔(x+1)(x-1-1)=0
⇔(x+1)(x-2)=0
⇔\(\left[ \begin{array}{l}x=2\\x=-1\end{array} \right.\)
