Question

求一道数学题的解

已知X的2次方+3X-6=0
求（1）6X的2次方+18X-5的值
（2）负四分之一X的2次方-四分之三X+1的值

十分抱歉，只能用文字了

Answer 1

(1)x^2 + 3x - 6 = 0
6x^2 + 18x - 5 = 6x^2 + 18x - 36 + 31 = 6*(x^2 + 3x - 6) + 31 = 31
(2)-0.25x^2 - 0.75x + 1 = -0.25x^2 - 0.75x + 1.5 -0.5 = -0.25(x^2 + 3x - 6) - 0.5 = -0.5

Answer 2

x^2+3x-6=0
(1)6x^2+18x-5
(2)-1/4*x^2-3x/4+1
解：
x^2+3x-6=0
x^2+3x=6
(1)
6x^2+18x-5
=6(x^2+3x)-5
=6*6-5
=31
(2)
-1/4*x^2-3x/4+1
=-1/4(x^2+3x)+1
=-1/4*6+1
=-3/2+1
=-1/2

Answer 3

x^2+3x-6=0
6x^+18x-5=6x^+18x-36+31=0+31=31
-1/4 x^2-3/4 x+1=-1/4(x^2+3x-6)-1/2=-1/2

Answer 4

x²+3x-6=0
6x²+18x-5=6(x²+3x-5/6)=6(x²+3x-6+6-5/6)=6(x²+3x-6)+36-5=6×0+36-5=31
(-1/4)x²-(3/4)x+1=(-1/4)(x²+3x-4)=(-1/4)(x²+3x-6+2)=(-1/4)(x²+3x-6)-1/2=(-1/4)×0-1/2=-1/2