1) 2х+10-3х+6=10
х=6
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2) 10-2х-10х+15=1
-12х=-24
х=2
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3) х^2+2x при х=98:
98^2+2*98=9604+196=9800
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х^2+2x при х=-202 :
-202^2-2*202=40804-404=40400