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14 August, 16:27

Letf (x) = x + |2x - 5|. Find all solutions to the equationf (x) = 10. (Enter your answers as a comma-separated list. If an answer does not exist, enter DNE.) x = (b) Letg (x) = 4x - 6 + |x + 3|. Find all values of a which satisfy the equationg (a) = 3a + 9. (Enter your answers as a comma-separated list. If an answer does not exist, enter DNE.) a =

+5
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  1. 14 August, 20:05
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    Part 1 : Given equation,

    f (x) = x + |2x - 5|,

    We have,

    f (x) = 10,

    x + |2x - 5| = 10

    |2x - 5| = 10 - x

    2x - 5 = ± (10-x)

    Case 1 : 2x - 5 = 10 - x

    2x = 10 - x + 5

    2x + x = 15

    3x = 15

    ⇒ x = 5

    Case 2 : 2x - 5 = - 10 + x

    2x = - 10 + x + 5

    2x - x = - 5

    ⇒ x = - 5

    Thus, the value of x is 5 or - 5

    Part 2 : Given equation,

    g (x) = 4x - 6 + |x + 3|,

    Put x = a,

    g (a) = 4a - 6 + |a + 3|

    We have, g (a) = 3a + 9

    4a - 6 + |a+3|=3a + 9

    4a + |a + 3 | = 3a + 9 + 6

    |a + 3| = 3a - 4a + 15

    |a + 3| = - a + 15

    ⇒ a + 3 = ± (-a + 15)

    Case 1 : a + 3 = - a + 15

    a = - a + 15 - 3

    a + a = 12

    2a = 12

    ⇒ a = 6

    Case 2 : a + 3 = a - 15

    a = a - 15 - 3

    a - a = - 18

    0 = - 18 (False)

    Thus, the value of a is 6.
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