Question

因式分解： （x平方-1）（x平方+2）-70

Answer 1

( x" - 1 )( x" + 2 ) - 70

先用平方差算一算

= ( x" - 1 )( x" + 1 ) + ( x" - 1 ) - 70

= ( x" )" - 1 + x" - 1 - 70

= x^4 + x" - 72

分解因式

= ( x" )" + 9x" - 8x" - 72

= x"( x" + 9 ) - 8( x" + 9 )

= ( x" + 9 )( x" - 8 )