1. Which of the following mathematical sentences are quadratic equations?

a. 2(x-1)²=1
b. 5n²+11 ≤n+20
c. 2x²-x≥ 3
d. 2x²- 5x+12≥0
e. x²-18x+80=0
f. - x²-7x+21<0
g. x²-2=0
h. m²-1≤ 2m²+3
i. p²+P14-7≤ 2P+3
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