多项式的值与x所取的值无关,即该多项式不含有带x的项,则x的对应项系数之和为0
(2x的2次方+ax-y+6)-(2bx的2次方-3x+5y-1)
=(2x^2 + ax - y + 6) - ( 2bx^2 - 3x + 5y - 1)
= 2x^2 + ax - y + 6 - 2bx^2 + 3x - 5y + 1
= ( 2x^2 - 2bx^2 ) + ( ax + 3x )-( y + 5y )+( 6 + 1 )
= 2x^2( 1 - b ) + ( a + 3 )x - 6y + 7
所以 1 - b = 0 ,a + 3 = 0
那么 b = 1 ,a = -3
因此,多项式3分之1a的3次方-2b的2次方-(4分之1a的3次方-3b的2次方)
= (1/3)a * a * a - 2 * b * b - (1/4)a * a * a + 3 * b * b
= (1/12)a * a * a + b * b
= 1/12 * ( -3 ) * ( -3 ) *( -3 ) + 1 * 1
= -9/4 + 1
= - 5/4