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Eighth grade math exercise book 1
1, x2+9x+20=0 (where x2 refers to the square of x)

2、

(1), 1\2x squared +7/2x+5=0, both sides are simplified by 2, x2+7x+ 10=0, factorization (x+2)(x+5)=0, and x=-2.

(2), 0. 1x squared-1.2=0.4x, both sides are multiplied by 10 to simplify, x2- 12=4x, and 4x is moved to the left of the equation: x2-4x- 12=0.