Problems based on Numbers Test 4

Question : 5 of 40

Marks: +1, -0

If x and y are positive integers such that x > y, which of the following will be value of

2x - 5y

, if

7x^ 2 = -77x + 294

and

3y^2=54y-51 .

Solution:

7x^2=-77x+294

x^2=-11x+42

⇒x^2+11x-42=0

x^2+14x-3x-42=0

(x+14)(x-3)=0

⇒ x = -14

and 3
Since x is positive integer, x = 3.

3y^2=54y-51

y^2=18y-17

⇒y^2-18y+17=0

y^2-17y-y+17=0

(y-17)(y-1)=0

y=17

and 1
Since y is smaller than x, y = 1

2x - 5y = 2(3) - 5(1)

= 6 - 5 = 1 .

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