left ( ((begin(array)(ll) (y=x+2left ( 1 right )) \ (z=2yleft ( 2 right )) \ (100z+10y+x-left ( (100x+10y+z) right )=495left ( 3 right )) end(array))) right . left ( 3 right )式可化为 z-x=5left ( 4 right ) 把left ( 2 right )代入left ( 4 right ...
left(begin(array)l3x+4z=7①\ 2x+3y+z=9②\ 5x-9y+7z=-6③end(array)right. ②times 3+③得11x+10z=21④ ④times 2-①times 5得7x=7 解得x=1 把x=1代入①得3+4z=7 解得z=1 把x=1,z=1代入②得2+3y+1=9 解得y=2 方程组的解为left(begin(array)lx=1\ y=2\ z=1...
解答解:由\left\{\begin{array}{l}x=-3+2cosθ\\ y=4+2sinθ\end{array}\left\{\begin{array}{l}x=-3+2cosθ\\ y=4+2sinθ\end{array},得{x+3=2cosθy−4=2sinθ{x+3=2cosθy−4=2sinθ,两式平方作和得,(x+3)2+(y-4)2=4; ...
10.若整数a使关于x的不等式组\left\{\begin{array}{l}\frac{x+1}{2}≤\frac{2x+5}{6}\\ x-2>a\end{array}\left\{\begin{array}{l}\frac{x+1}{2}≤\frac{2x+5}{6}\\ x-2>a\end{array}至少有4个整数解,且使关于x的分式方程12−axx+212−axx+2=2有整数解,那么所有满足条件的a...
解方程组:left ( ((begin(array)(ll) (2x+4y=100①) \ (x+y=36②) end(array))) right . ①-②times 2,得2y=28, therefore y=14. 把y=14代入②,得x+14=36, therefore x=22. therefore 方程组的解为left ( ((begin(array)(ll) (x=22) \ (y=14) end(array))) right .. 即...
解析 left ( ((begin(array)(ll) (1400=40k+b①) \ (3600=80k+b②) end(array))) right . ②-①,得:40k=2200 解之,得:k=55 把k=55代入①,得:1400=40times 55+b 解之,得:b=-800 therefore 方程组的解为:left ( ((begin(array)(ll) (k=55) \ (b=-800) end(array))) righ...
【规定】\left|\begin{array}{ll}a& b\\ c& d\end{array}\right|=ad-bc.【理解】例如:\left|\begin{array}{ll}3& 2\\ 1& -3\end{array}\right|=3\times \left(\begin{array}{l}-3\end{array}\right)-2\times 1=-11.【应用】先化简,再求值:\left|\begin{array}{ll}xy-3{x}^{...
6.函数f(x)=\left\{{\begin{array}{l}{(3-a)x-1,x<2}\\{{{log}_a}(x-1)+1,x≥2}\end{array}}\left\{{\begin{array}{l}{(3-a)x-1,x<2}\\{{{log}_a}(x-1)+1,x≥2}\end{array}},若f(x)是R上的增函数,则a的取值范围为( ) ...
解答 解:作出函数f(x)=\left\{\begin{array}{l}{{x^2}-2x,x≥-1}\\{x+4,x<-1}\end{array}}\left\{\begin{array}{l}{{x^2}-2x,x≥-1}\\{x+4,x<-1}\end{array}}的图象如图, 函数y=x+4 在 x∈(-∞,-1)上单调增,其值域为(-∞,3]; ...
left ( 4 right )-left ( 1 right )得: c=5 left ( 4 right )-left ( 2 right )得: b=3 left ( 4 right )-left ( 3 right )得: a=2 therefore left ( ((begin(array)(ll) (a=2) \ (b=3) \ (c=5) end(array))) right .反馈...