Introduction to Proof: Informal and Two Column Proofs

think icon Think & Click: Proof

Now, you try. Complete the Think & Click activity by looking at each problem below, thinking about it, and then clicking on the question to reveal the solution.

Give reasons for each step of the proof that given 2(x − 4) + 7 = 5, x = 3

Step 1:     2x – 8 + 7 = 5

Reason solution

Step 2:     2x – 1 = 5

Reason solution

Step 3:     2x = 6

Reason solution

Step 4:     x = 3

Reason solution