Identify Variables: Identify a, b, and c in the quadratic expression z2+8z+15. The quadratic expression is in the standard form z2+bz+c, where a=1, b=8, and c=15.
Find Multiplying Numbers: Find two numbers that multiply to c (15) and add up to b (8).We need to find two numbers that multiply together to give 15 and when added together give 8. The numbers 3 and 5 satisfy these conditions because 3×5=15 and 3+5=8.
Write Factored Form: Write the factored form using the two numbers found in Step 2.The factored form of the quadratic expression is (z+3)(z+5), because these two binomials multiply out to the original quadratic expression z2+8z+15.
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