X squared -9 ------------------- 3x+9
1 answer:
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Answer:
x = 10
Step-by-step explanation:
3x - 9 = 21
add 9 on both sides:
⇒ 3x - 9 + 9 = 21 + 9
⇒ 3x = 30
divide 3 on both sides:
⇒
⇒ x = 10
to check answer, substitute x by 10 on the original equation:
⇒ 3x - 9 = 21
⇒ 3 x 10 - 9 = 21
⇒30 - 9 = 21
⇒ 21 = 21