cindy21
幼苗
共回答了15个问题采纳率:93.3% 举报
(1)y=2x^2 - 12x + 13
=2(x^2-6x)+13
=2(x^2-6x+9)+13-19
=2(x-3)^2-6 对称轴是X=3 顶点坐标是(3,-6)
(2)y= -5x^2+80x-319
=-5(x^2-16x)-319
=-5(x^2-16x+64)-319+320
=-5(x^2-16x+64)+1
=-5(X-8)^2+1 X=8 (8,1)
(3) 先化简 得y=2x^2-5x+2
=2(x-5/4)^2-9/8 x=5/4 (5/4 ,-9/8)
(4) 先化简 得y=-6x^2+9x+6
=-6(x-3/4)^2+6+27/8
x=3/4 (3/4,75/8)
1年前
10