已知,圆C:x2+y2-8x+12=0,直线l:ax+y+2a=0.(1)当a为何值时,直线l与圆C相切 （2）当直线l与圆C相交于A,B两点,且|AB|=2根号2时,求直线l的方程.你的答案不对 不好意思

已知,圆C:x2+y2-8x+12=0,直线l:ax+y+2a=0.(1)当a为何值时,直线l与圆C相切 （2）当直线l与圆C相交于A,B两点,且|AB|=2根号2时,求直线l的方程.你的答案不对 不好意思
已知,圆C:x2+y2-8x+12=0,直线l:ax+y+2a=0.(1)当a为何值时,直线l与圆C相切 （2）当直线l与圆C相交于A,B两点,且|AB|=2根号2时,求直线l的方程.
你的答案不对 不好意思

已知,圆C:x2+y2-8x+12=0,直线l:ax+y+2a=0.(1)当a为何值时,直线l与圆C相切 （2）当直线l与圆C相交于A,B两点,且|AB|=2根号2时,求直线l的方程.你的答案不对 不好意思
x²-8x+16+y²=4
(x-4)²+y²=4
表示圆心为（4,0）半径为2的圆
根据题意
圆心到直线的距离为半径时相切
｜4a+2a｜/√(a²+1)=2
｜3a｜=√(a²+1)
9a²=a²+1
a²=1/8
a=±√2/4
(2)1/2|AB|=√2,半径为2
根据勾股定理,我们知道圆心到直线的距离为√2
所以有｜4a+2a｜/√(a²+1)=√2
36a²=2a²+2
17a²=1
a=±1/√17
直线为1/√17x+y+2/√17=0即x+√17y+2=0
或-1/√17x+y-2/√17=0即x-√17y+2=0
你说的哪一个不对?
你题目的数据准确吗?

这个题要自己想呀

我看楼上对的

According to Xinhua News Agency Xinhua China Banking Regulatory Commission Chairman Liu pointed out 20,nike heels sandals, the banking financial institutions to strengthen the land reserve loan manage...

全部展开

According to Xinhua News Agency Xinhua China Banking Regulatory Commission Chairman Liu pointed out 20,nike heels sandals, the banking financial institutions to strengthen the land reserve loan management,black heels, and control real estate development loan risk; the implementation of dynamic,jordan boots, differentiated management of individual mortgage policies strictly limit variety of names,nike heels, real estate and speculative; quarter of medium-sized banks to carry out real estate loans according to the pressure test. Banking Regulatory Commission Liu in 2010,dunk sb heels, a second briefing on economic and financial analysis of the situation that the banking financial institutions to effectively control the annual incremental credit, credit to grasp the rhythm,dunk heels, to optimize credit structure; implementation Scientific assessment and incentives; full implementation of the "three ways, a guide" ("Interim Measures on Management of fixed asset loans,cheap jordan heels," "working capital loan management approach,nike heels for women," "Personal Loans" and "the project finance guidelines"); accordance with the "per-packet Open,nike dunk heels, transaction verification,blue high heels, re-evaluation,nike jordan heels, rectification preservation "requirement,women jordan heels, a solid job of local government financing platform for credit risk management and control work; must be done before the end of the third quarter of accurate classification,Red high heels, set aside enough provisions, basically completed during the year write-off of bad debts , so that account sales,jordan heels shoes, storage case, right in, and continued attention to time,micheal jordan heels, in the preservation and recovery period.

收起