①x2-8x-7=0②x2+14x-15=0③t2-(2/3)t-(8/9)=0④4(x+3)2-9(x-2)2=0

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①x2-8x-7=0②x2+14x-15=0③t2-(2/3)t-(8/9)=0④4(x+3)2-9(x-2)2=0
①x2-8x-7=0②x2+14x-15=0③t2-(2/3)t-(8/9)=0④4(x+3)2-9(x-2)2=0

①x2-8x-7=0②x2+14x-15=0③t2-(2/3)t-(8/9)=0④4(x+3)2-9(x-2)2=0
①x2-8x-7=0
Δ=64+4×7=64+28=92;
x=(8±2√23)/2=4±√23;
(②x2+14x-15=0
(x+15)(x-1)=0;
x=1或x=-15；
③t2-(2/3)t-(8/9)=0
(t-4/3)(t+2/3)=0;
t=4/3或t=-2/3;
④4(x+3)2-9(x-2)2=0
4(x+3)²=9(x-2)²;
2(x+3)=±3(x-2);
2x+6=3x-2或2x+6=-3x+2；
x=8或x=-4/5;

x2-3x-1=0,求①x2 1/x2;②x2-1/x2 x2-8x+15=0　　　求两根 x2-5x+6=0　　　　求两根 注：x2是x2方啊 分解因式下：X4-2X2-8 X2-3XY+2Y2 2X2-7X+3 X2+2X-15-AX-5A 解方程：1999X2-2000X+1=0 X2-14X+13=01949X2-1999X+50=0 7/x2+x+1/x2-x=6/x2-1 7/x2+x+1/x2-x=0 (x2+5x+5)/(x2+5x+6)-(x2+8x+14)/(x2+8x+15)化简 ①x2-8x-7=0②x2+14x-15=0③t2-(2/3)t-(8/9)=0④4(x+3)2-9(x-2)2=0 ①x2-x-6＞0 ② x2+2x-15＜0 ③ x2+7x+12≥0要画函数 ①2x2-6x+1=0②3x2+8x-1=0③2x2-3x=2④3x2=-6x+8⑤2x2-7x+2的最小值⑥-3x²＋5x＋1的最大值 x2-3x+1=0 x2/(x4-x2+1) x2-5x+1=0则x2+x2/1 【x2-2x+2][x2-2x-7]+8=0的解 用配方法解下列方程①x2-2x-2=0②x2+8x-9=0③2x2+1=-3x④3x2-6x+4=0 X2-X+1/4=0 x2+8x+15=0 2x2+5x+2=0 x2-5=4x 用配方法 2(x-3)2=x2-9用分解因式法 设3x²+2x-3=0,两根为x1,x2,求①x2/x1 + x1/x2 ②x1^2+x2^2-4x1x2 设3x²+2x-3=0,两根为x1,x2,求①x2/x1 + x1/x2 ②x1^2+x2^2-4x1x2 解方程 2/(x2-x)+6/(1-x2)=7/(x2+x)x2为的平方 解方程：X2--1/8(X2+2X)+X2+2X/3(X2--1)=11