Q 31 :

The line passing through the point of intersection of x+y=2x-y=0 and is parallel to x+2y=5 is ax+by=c, then value of a+b+c is _________.



(6)

Required equation of line which is parallel to given line x+2y=5 is x+2y+k=0               (i)

Given equations of lines are

          x+y=2                                                             (ii)

          x-y=0                                                             (iii)

Adding (ii) and (iii), we get 2x=2x=1

Substituting x=1 in (iii), we get y=1

   Point of intersection is (1,1)

Substituting x=1, y=1 in (i), we get

1+2+k=0k=-3

   Required equation of line is x+2y=3

Here, a=1, b=2 and c=3

  a+b+c=1+2+3=6



Q 32 :

A1,A2,,An are points on the line y=x lying in the positive quadrant such that OAn=n·OAn-1, O being the origin. If OA1=1 and the coordinates of An are (25202,25202), then the value of n is _______.



(7)

We have, OAn=n·OAn-1

=n(n-1)·OAn-2==n!·OA1=n!

  OAn=n!

2×25202=n!

n!=5040

n=7



Q 33 :

The area of the rhombus ABCD is 24. The equation of the diagonal BD is 4x+3y+2=0 and A=(3, 2). The length of the side of the rhombus is ______.



(5)

Let AC and BD intersect at P.

Now, AP=12+6+216+9=4

  Area of ABD=AP×BP=242=12BP=3

  AB=AP2+BP2=5



Q 34 :

In ΔABC, the equation of altitudes AM and BN are x+5y-3=0, x+y-k=0. If the altitude CL is given by 3x-y-1=0, then k= ______.



(1)

Solving the altitudes AM and CL, we get

Orthocentre=(12,12)  lies on x+y-k=0k=1



Q 35 :

The centroid of the triangle formed by (a,b), (b,c), (c,a) is the origin and a3+b3+c3=kabc, then k is _______.



(3)

Given,  G=(a+b+c3,a+b+c3)=(0,0)

a+b+c=0

a3+b3+c3=3abc

k=3