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How do you solve d=7a d=4a+30

1 Answer

5 votes

Answer:

a = 10 , d = 70

Explanation:

Solve the following system:

{d = 7 a | (equation 1)

{d = 4 a + 30 | (equation 2)

Express the system in standard form:

{-(7 a) + d = 0 | (equation 1)

{-(4 a) + d = 30 | (equation 2)

Subtract 4/7 × (equation 1) from equation 2:

{-(7 a) + d = 0 | (equation 1)

{0 a+(3 d)/7 = 30 | (equation 2)

Multiply equation 2 by 7/3:

{-(7 a) + d = 0 | (equation 1)

{0 a+d = 70 | (equation 2)

Subtract equation 2 from equation 1:

{-(7 a)+0 d = -70 | (equation 1)

{0 a+d = 70 | (equation 2)

Divide equation 1 by -7:

{a+0 d = 10 | (equation 1)

{0 a+d = 70 | (equation 2)

Collect results:

Answer: {a = 10 , d = 70

User Bruno Lange
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