What is the answer to 21=7|2u+3| ?

The answer to 21=7|2u+3| is u=-3\lor u=0

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21=7|2u+3|

21 = 7 ∣ 2 u + 3 ∣

u = - 3 or u = 0

Solution steps

21 = 7 ∣ 2 u + 3 ∣

Switch sides

7 ∣ 2 u + 3 ∣ = 21

Divide both sides by

7

∣ 2 u + 3 ∣ = 3

Apply absolute rule: If

∣ u ∣ = a, a > 0

then

u = a

u = - a

2 u + 3 = - 3 or 2 u + 3 = 3

2 u + 3 = - 3 or 2 u + 3 = 3

u = - 3 or u = 0

∣ 6 y - 18 ∣ = 6

∣ 9 x - 10 ∣ = 17

∣ - 45 x - 2 ∣ + 9 = 4

- 6 + 6 ∣ x - 6 ∣ = - 36

\frac{y}{2} = 11