A:{5x+3y=5+211x+5y=9×0.9
B:{5x+3y=5+211x+5y=9÷0.9
C:{5x+3y=5−211x+5y=9×0.9
D:{5x+3y=5−211x+5y=9÷0.9
二次函数y=x2+2x-3的图象的顶点坐标是( )