integral (x + 3)(4x-5) dx....

∫x^n dx = 1/(n + 1) . x^(n + 1) + C

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∫(x + 3)(4x - 5) dx
= ∫(x² + 7x - 15) dx
= x³/3 + 7x²/2 - 15x + C
= 1/3 x³ + 7/2 x² - 15x + C