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> 今年的全国助残日这天,某单位的青年志愿者到距单位6千米的福利院参加“爱心捐助活动”。一部分人步行,另一部分人骑自行车,他们沿相同的路线前往。如图,l1、l2分别表示步行-九年级数学
今年的全国助残日这天,某单位的青年志愿者到距单位6千米的福利院参加“爱心捐助活动”。一部分人步行,另一部分人骑自行车,他们沿相同的路线前往。如图,l1、l2分别表示步行-九年级数学
题目简介
今年的全国助残日这天,某单位的青年志愿者到距单位6千米的福利院参加“爱心捐助活动”。一部分人步行,另一部分人骑自行车,他们沿相同的路线前往。如图,l1、l2分别表示步行-九年级数学
题目详情
今年的全国助残日这天,某单位的青年志愿者到距单位6千米的福利院参加“爱心捐助活动”。一部分人步行,另一部分人骑自行车,他们沿相同的路线前往。如图,
l
1
、
l
2
分别表示步行和骑自行车的人前往目的地所走的路程y(千米)随时间x(分钟)变化的函数图象。
(1)分别求
l
1
、
l
2
的函数表达式;
(2)求骑车的人用多长时间追上步行的人.
题型:解答题
难度:中档
来源:四川省模拟题
答案
解:(1)设
l
1的表达式为y1=k1x ,由图象知
l
1过点(60,6)
∴60k1=6,k1=
∴y1=
x
设
l
2的表达式为y2=k2x+b2 ,由图象知l2过点(30,0)和(50,6)两点
∴
解得
∴y2=
x-9
(2)当骑车的人追上步行的人时,y1=y2,即
x=
x-9 ,x= 45
45-30=15(分钟)
答:骑车的人用15分钟追上步行的人。
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题目简介
今年的全国助残日这天,某单位的青年志愿者到距单位6千米的福利院参加“爱心捐助活动”。一部分人步行,另一部分人骑自行车,他们沿相同的路线前往。如图,l1、l2分别表示步行-九年级数学
题目详情
(1)分别求l1、l2的函数表达式;
(2)求骑车的人用多长时间追上步行的人.
答案
∴60k1=6,k1=
∴y1=
设l2的表达式为y2=k2x+b2 ,由图象知l2过点(30,0)和(50,6)两点
∴
∴y2=
(2)当骑车的人追上步行的人时,y1=y2,即
45-30=15(分钟)
答:骑车的人用15分钟追上步行的人。